Caitlin Snow


 * For her Earth Two counterpart, see Caitlin Snow (Earth Two).
 * For her Earth Fifty counterpart, see Caitlin Snow (alternate).

"They call me Killer Frost. Let me show you why."

- Killer Frost to Cicada

Dr. Caitlin "Cait" Snow (born February 28, 2362) is a female Human in the 24th century who is a bio-engineer at S.T.A.R. Labs and a former scientist at Mercury Labs. She was working during the particle accelerator disaster and tended to Barry Allen during his coma with Cisco Ramon until he woke up. After he began his crusade as "The Flash" Caitlin became a member of his team with Cisco and Dr. "Harrison Wells", before discovering the latter's true identity as Eobard Thawne, and provides medical support for the team. Caitlin is the daughter of the late Dr. Thomas Snow and Dr. Carla Tannhauser, the wife of the late Ronnie Raymond, and close friends with Cisco, Barry, Felicity Smoak, Typhuss James Kira, Professor Martin Stein, and Iris West. She is also the former lover of "Jay Garrick", before discovering his true identity as Hunter Zolomon, and the ex-girlfriend of Julian Albert.

In the Flashpoint timeline, Caitlin is not a scientist but a doctor who is unwillingly brought into Ramon Industries by Barry to help him restore the timeline. Following Barry's attempt to restore the timeline, Caitlin is once again a scientist at S.T.A.R. Labs, but she is also a meta-human with abilities similar to her Earth-2 doppelgänger, who she is afraid of becoming like. However, it was later revealed that she was a dormant meta-human all along due to her father using an experimental ALS treatment on her, when she was 10. After being taken over by her rising anger while using her meta-human powers and losing control of her emotions, Caitlin briefly started going by her doppelgänger's name, Killer Frost.

After suffering a clinical death from a seizure and subsequently being revived by her regenerative powers, her biochemistry was altered, culminating in her becoming fully consumed by her anger as Killer Frost, later encountering and allying with Savitar after the proclaimed speedster god reveals his true identity as a future version of Barry Allen. Later, between Cisco giving Caitlin the choice to cure herself rather than force it on her and watching Savitar nearly kill him, Caitlin finally regained her true personality and control of her powers. Despite this, Caitlin decided not to take the cure. Feeling lost to her own identity, Caitlin left Team Flash on good terms to rediscover herself. Six months later, having seemingly come to terms with her mistakes as Killer Frost, Caitlin finally decided to re-join Team Flash, only to discover that her Killer Frost-side had returned.

Shortly after returning to Team Flash, Caitlin once again began to struggle with her Killer Frost side and eventually lost control. Iris convinced both Caitlin and Killer Frost that they could try to be the same person instead of choosing one life or the other. As such, when preparing to serve as back up to Barry along with Cisco she stated "Snow and Frost standing by" emphasizing that both Caitlin and Killer Frost were prepared to work together to help. When Nazis from Earth-X tried to invade Earth-1, she aided her friends in the battle that followed, earning Mick Rory's affection. In a battle against Clifford DeVoe, she lost her Killer Frost side as a result of DeVoe using Dominic Lanse's powers to create a mental block. After defeating Siren-X from Earth-X, Caitlin discovers that Killer Frost is still inside her, without the presence of dark matter. She later learns, from a suppressed memory, that Killer Frost has been with her since childhood, before she was exposed to the dark matter released by the particle accelerator.

After defeating DeVoe and getting Ralph back, he discovered that Caitlin father's death certificate was a fake and that he was actually alive. Barry, Cisco and Caitlin eventually found him hiding out in an old warehouse. However, he later revealed himself to be Thomas' evil alternate personality and attempted to kill the team and take over Thomas' body completely. During the fight, Caitlin managed to break through the mental block that DeVoe had created and regain Killer Frost.

Early life
From a young age, Caitlin idolized her parents who were both doctors and was inspired to follow in their footsteps. Growing up Caitlin practiced the Hippocratic oath and was obsessed with it. She grew to value life so much she wouldn't even let anyone step on a bug if she could help it. From a young age Caitlin was very close with her father but he suffered from multiple sclerosis. Her mother Carla Tannhauser tried to save him as he fought it for years but he eventually died, much to Caitlin's heartache. Following her father's death Carla began focusing only on her work as a way to cope with losing her husband, but her neglect of Caitlin left them estranged for several years.

In high school, Caitlin was bullied by Lexi LaRoche who put chewed bubble gum in her hair.

In adult years Caitlin became a trained neurosurgeon but was still estranged from her mother. Despite being estranged Carla still offered Caitlin a position at Tannhauser Industries but Caitlin wanted to make a name for herself and declined. Some time before 2377 Caitlin was hired at S.T.A.R. Labs by Dr. "Harrison Wells". Sometime after this she met Ronnie Raymond a structural engineer who in contrast to Caitlin's guarded outlook was more outgoing. Caitlin would later describe them as being "Fire and Ice". Despite being very different the two fell deeply in love and started dating. Though she enjoyed working at S.T.A.R. Labs she, like most employees, was often irritated by Dr. Wells' protege Hartley Rathaway.

Around 2378, Caitlin went out of town for their one year anniversary with Ronnie. Before leaving she met newly employed engineer Cisco Ramon after witnessing him debate engineering with Hartley. Cisco and Caitlin became close friends and he would consider her and Ronnie family, as he was estranged from his own and looked up to the couple. Eventually Ronnie proposed to Caitlin and she accepted. However she apparently never told her mother as she wouldn't even be aware Ronnie existed until over 1 year after his actual death.

Return of Killer Frost
Whether as the result of Flashpoint or not, Caitlin developed cryokinesis meta-human powers akin to those of her Earth Two counterpart. She kept this a secret from the rest of the team, using them to help Barry escape Mirror Master's mirror trap. However, she later noticed while taking a shower that some of her hair turned pale blonde; she promptly cut off the altered hair to hide her powers. Desperate to understand what was happening to her, Caitlin visited her mother but was quickly annoyed when she asked if Caitlin had received her birthday card which she confirmed, in April, presumably a significant amount of time before or after it. Caitlin inquired how to get an appointment with her for a friend, not ready to reveal her secret, but as Carla coldly walked her through the procedures Caitlin angrily froze her desk and revealed she was the patient. Carla subsequently canceled all her appointments for the day and readied various tests for Caitlin. While preparing she met Carla's assistant Nigel. Caitlin was brought down to the facility's testing lab for molecular motion where she revealed a shaft made of solid tungsten, heated to over 2000 degrees centigrade. Carla asked Caitlin to freeze it in order to determine how to reverse what's happening to her. To her horror she froze it solid within seconds. After Caitlin revealed the origin of her powers, she and Carla fought over Caitlin working at S.T.A.R. Labs rather than Tannhauser Industries, which Caitlin reminded her was because she desired to make a name for herself. Before they could argue further Nigel came back with the results and revealed that Caitlin had not just frozen the tungsten but had absorbed all the energy it was emitting. However Caitlin was frustrated when she heard them talking about how her power could benefit their pursuits rather than offer sympathies. When Carla began taking blood samples Caitlin, finally having had enough, confronted her over he seemingly lack of care for her well-being and how she hasn't expressed any concern over her well being since her father died. Carla defended that she tried to save him and reminded Caitlin that she ran away but Caitlin told Carla that she had to because she wouldn't even so much as look at her. Carla accepted Caitlin's anguish and admitted that she got consumed in her work out of grief but scolded Caitlin, believing she didn't know what that kind of loss feels like. Outraged, Caitlin told Carla about Ronnie, who Carla didn't even seem to be aware of.

Having had enough, Caitlin decided to leave but Nigel trapped her in the facility wanting to exploit her powers for himself. As he grabbed her Caitlin's inner Killer Frost persona was released in a fit of pure rage and she grabbed Nigel and froze his arm solid. Carla came into confront her, and Killer Frost ordered her mother to move, but Carla offered her apologizes, acknowledging that she wasn't much of a mother, but was steadfast that she didn't raise a killer, managing to talk her out of killing Nigel as mother and daughter hugged. Caitlin returned to help Team Flash stop the supposed monster roaming the city, only for it to be a hologram. Caitlin later told Cisco about visiting her mother and he commended her for trying to make amends with her family. Later Carla contacted Caitlin via webcam and told her that her results proved unfruitful; that Caitlin's biology was rapidly changing and the more she used her powers the less control she'd have. After hearing this, Killer Frost's anger emerged again, as Caitlin has accidentally frozen her desktop monitor, horrified to see that she was losing control over her emotions along with her growing meta-human powers. Worried of her powers, Caitlin stole power dampeners from S.T.A.R. Labs, something that Cisco thought to blame on H.R. Wells. She was seen wearing the dampeners during an attack of the meta-human Shade. After Cisco accidentally vibed Caitlin in the guise of Killer Frost, he forced her to reveal the truth about her powers to the team.

Caitlin said she wouldn't save Barry from Savitar, for fear of using her powers and unleashing her Killer Frost side, and only went after Iris begged her. And after using her powers to save Barry from Savitar; unfortunately, she ended up dominated by her worry and anger, turning into Killer Frost. She went after Dr. Alchemy in an attempt to rid herself of her powers. She tricked Joe into believing that Wally has emerged from his cocoon, trying to divert Joe from the interrogation of one of the acolytes of Alchemy. She tortured the acolyte, but before she could extract any useful information, Caitlin was forced to flee by approaching SCIS officers, leaving the acolyte frozen. Still obsessed with finding Alchemy, Killer Frost kidnapped Julian Albert, forcing him to create a search algorithm to find Savitar's acolytes. Julian succeeded in locating a member of Alchemy's cult, but also alerted the SCIS to Killer Frost's location, as she tried to kill him. However, The Flash arrived and attempted to talk Caitlin down, even knocking out Albert to permit them to speak freely. Unfortunately, Caitlin was unable to control her powers; too far gone and panicked, she stabbed him in the leg and went after one of the acolytes, Craig. Upon arriving, she threatened the man's family, forcing him to comply. He informed Killer Frost that he didn't know where Alchemy was, or who he was, but only that Alchemy was merely another acolyte of Savitar who had shown them the future where, among other things, Caitlin had become Killer Frost. However, before she could press for more info on how to take away her powers, Vibe arrived and, like Barry, attempted to talk her down, but Killer Frost attacked Cisco. Barry then arrived on the scene and knocked Killer Frost to the ground. Unwilling to surrender, Killer Frost gave Barry a kiss, using her powers to freeze him solid. Luckily, Cisco was fast enough to smite her with a Vibe burst, knocking Killer Frost unconscious. Upon waking up in the Pipeline, Killer Frost attempted to convince Team Flash she was back to normal, to no avail. She then made an offer of leaving them alone, if they release her and allow her to go on her way. But Barry refused to abandon her, angering Frost. She yelled at him, blaming Barry rightly for everything bad that happened to the team after Flashpoint. Barry returned, asking for Caitlin's help with a freed Wally West, who couldn't maintain control over his powers. Killer Frost taunted Barry, who released her on one condition: if she wanted to leave, she had to kill him. Killer Frost threatened to do so, producing an icicle, but was unable to kill her friend. Crying, Caitlin finally snapped out of her anger and she hugged him, horrified at her actions. Barry comforted her and she went back with him, assisting the team in returning Wally to normal (albeit now with Super-Speed). Barry quit his job to save Caitlin from a life in prison after pleading with a furious Julian Albert, who would not be swayed to keep her secret unless Barry resigned from his work as a CSI, and she never thanked him for this.

Invasion
During a joint mission with the Legends to stop the Dominators' invasion, Caitlin mostly partnered up with Professor Martin Stein, who encouraged her to learn how to control her powers, instead of denying them, just like he did as Firestorm. On her end, Caitlin helped Professor Stein to accept his daughter, Lily Stein, who was born as a result of an accidental temporal aberration.

Defeating Alchemy
After the Flash has defeated Alchemy and took the Philosopher's Stone to S.T.A.R. Labs safe in its compartment box, Savitar tried to manipulate Cisco Ramon into taking the stone for himself and releasing him, appearing to Cisco in the guise of his late brother, Dante Ramon. Despite being threatened by Cisco not to approach him, Caitlin managed to talk him down and persuade to hide the Brahmastra, stopping Savitar again. Later on, Caitlin was present when Team Flash communicated with Savitar, possessing the body of Julian Albert. She was worried as he claimed a prophecy for Team Flash, saying that one of them would fall, the other betray them, and the other would suffer a fate worse than death. After this ordeal, Caitlin encouraged Julian to come celebrate Christmas together with Team Flash at West house, later on congratulating the CSI specialist when he came to the party after all. Showing Cisco that she took Martin Stein's advice to heart and started to practice control over her powers, Caitlin removed her power dampener and produced an icy mist with her hand, turning a raincloud above West house into a cloud of white snow.

Attack on S.T.A.R Labs
A mysterious future villain of the Flash named Abra Kadabra appeared, stealing from several tech companies in an attempt to build a timeship to return to the 64th century. Abra Kadabra soon found himself chased after by the Flash and Gypsy, escaping, but not before telling Flash that he knew Savitar's name.

Sometime later, he teleported into S.T.A.R Labs and ambushed Caitlin, Julian and Joe West, but was soon apprehended by the Flash and locked up in the Pipeline, taunting the team about his knowledge of Savitar. There, he told Joe that if he let him escape from Gypsy, he promised to reveal Savitar's name so the team could save Iris. Joe agreed, and set him free, but Kadabra betrayed him, claiming that the terms of the agreement had changed. He then went to collect a mysterious future power source from the Time Vault, and set off an explosive as the trio attempted to chase after him upon his escape. The resulting explosion impaled Caitlin's side with shrapnel. Team Flash took her to the med bay and helped her onto the bed. Caitlin showed signs of physical pain, as she was breathing heavily and moaning. Cisco tried to stop the bleeding with a T-shirt while the team decided how they was going to help her. Julian X-rayed her and found she had bits of metal wedged inside her that needed to come out. Caitlin refused to go to the hospital as they will find out about her Killer Frost identity. Iris told the team that Caitlin couldn't operate on herself but Caitlin said she could if she had a mirror, she could talk someone through the surgery. Soon after Caitlin talked Julian though her own surgery. Iris helped stop the bleeding as Julian operated. As Julian came to the last piece of metal he found that it was stuck, as he tried to get it out, Caitlin's heart rate began to increase dangerously, causing Cisco to worry. Julian told her it was going to hurt as he pulled the metal out, Caitlin screamed in severe pain before becoming light headed and telling Julian to stitch her up as she was going to pass out. Not too long after she woke up in the med bay bed with Julien holding her hand. Julian told her how brave he thought she was before getting up to kiss her, but pausing out of fear of hurting her. Later that day, Cisco was alone with Caitlin. She seemed to be recovering well, but as they were talking, Caitlin stopped mid-sentence and passed out. She started seizing. Cisco panicked and called for help. Julian came running in with H.R. and they tried to hold her down, but she suddenly stopped. Cisco put his hand above Caitlin's mouth and found that she wasn't breathing. Julian began giving her compressions and told Cisco to get the oxygen mask and place it over her mouth. They then tried electric shock, but everything was unsuccessful. Julian tried more compressions while Cisco continued giving her oxygen but Caitlin wasn't responding and they couldn't resuscitate her. Cisco started crying, realizing his best friend had died. Julian, distraught, ripped off Caitlin's necklace, hoping her meta-human powers could regenerate her. About 30 seconds later, she began breathing again. Caitlin's wound also healed instantly, but she emanated a cloud of mist, sending the team and herself flying. Once the cloud cleared, Caitlin had transformed into Killer Frost and attacked the team before escaping.

Alliance with Savitar
Caitlin wandered around in the snow, only to encounter Savitar. She asked if Savitar wanted to cure her, to bring Caitlin Snow back, but the armored villain wanted just the opposite. Caitlin then asked Savitar why should she trust him. To prove that he can be trusted, Savitar removed his armor and revealed himself as a future version of Barry. Seeing that, Caitlin agreed to do anything he wants.

She was sent by Savitar to the Central City University in order to kill future physicist Tracy Brand, however her attempt on the scientist's life was thwarted by the intervention of Barry and Cisco. She returned to Savitar to tell him of her failure. Savitar questioned Frost's loyalty by pondering the idea that there may be more Caitlin Snow still within her than she led him to believe, especially due to the fact that despite taking up the name Killer Frost she had not yet actually killed anyone. He then told her to once again try to kill Tracy with the promise that if she succeeded they could both be gods.

A few hours later she kidnapped Cecille at the West house and told Joe that the only way to spare Cecille's life would be to trade her for Tracy. At the site of the trade off she battled both Barry and Cisco before being overcome by Cisco's powers and knocked unconscious. Cisco then acquired a blood sample from her that Julian hoped could be key, due to Caitlin undergoing a full mutation into Killer Frost, to reversing the process and cure their friend. Before the team could return to Star Labs, to presumably lock Frost away in the Pipeline for their and her own safety, Savitar appeared and escaped with the still unconscious Killer Frost.

When Savitar lost his memory, Killer Frost realized that Team Flash erased Barry's memory to prevent the future Savitar is trying to create; but this also caused Wally to lose his powers. She offered them the hard choice of returning Barry's memory or leaving Central City vulnerable to attacks by meta-human criminals. Cisco encouraged her to remember being Caitlin Snow, which allowed her to help restore Barry's memory in surgery. She prepared to leave, with Julian confessing that he had fallen in love with her. This news briefly shocked Killer Frost, who coldly told the entire team she never loved them. When in the elevator, her eyes briefly returned to normal, showing that Killer Frost could be turned back into Caitlin.

In a news report on a screen reporting the arrest of Jared Morillo that Barry saw during his accidental trip to May 2390, a subheading read "Killer Frost still at large". While Barry succeeded in altering the circumstances of Morillo's arrest, with Wally defeating him instead of Barry in January instead, Caitlin's future remained the same. Barry later reveals to Joe that Caitlin's on the loose and they need to bring her in, prompting him to alert the CCPD. This causes the aforementioned headline.

Killer Frost was later seen talking to Savitar about his plans if he's really ready to end his former lover's life. He then stated that "It's either her or me", and that when the time comes she should be ready to do her part. When Savitar captured Iris HR Wells risked his life to stop him he switched appearances with her, so when Frost attacked them she didn't realize that she was actually taking back HR. Caitlin then met Vibe in a snowy forest area and said that she needs to "cure herself of Caitlin" and the only way to do that is to kill him. As the fight went on Killer Frost gained the upper hand. Right before Frost could finish off Cisco, Savitar appeared and stated she should keep him alive, as he needs him to modify the Speed Force Weapon. Later on, after Vibe finished making the modifications, Savitar ordered Caitlin to kill Cisco, which she tried to do, but Gypsy interfered and the two escaped.

Killer Frost then helped Savitar get rid of the Black Flash, and then used the weapon on the God of Speed. While interrupted by Team Flash, she took on Gypsy and Vibe but was subdued. Cisco then offered Killer Frost the choice to use the cure and become Caitlin again or remain in her current state. When Savitar attacked Cisco and attempted to kill him, Killer Frost, without using the cure, managed to take control of herself and let go of the mad persona. She attacked Savitar and watched his defeat by Barry and Iris. Caitlin later attended the funeral of HR Wells, where she met Julian and Cisco. She told them about her decision to leave, in the hope that she can rediscover herself. They bid each other goodbyes, and departed on good terms.

Rediscovery and return
Trying to find her own way in life, Caitlin left Team Flash and journeyed away. Keeping a low profile, Caitlin didn't use her credentials to get a prominent job, instead becoming a bartender. During her stay away from S.T.A.R. Labs, Caitlin was contacted by Matthew Norvock, a member of Amunet Black's organization, and worked for them as Amunet's henchwoman. In exchange, Amunet used a transmodular genetic splicer, a piece of black market technology, to apparently split Caitlin and Killer Frost. During Samuroid's attack on Central City Cisco vibed Caitlin's location and visited the bar she worked in. He managed to convince her to return back to the team, where she helped Cisco in locating and later diagnosing Barry, much to Iris's hatred. Rejoining the team, Caitlin worked on helping to get Barry back to sanity, including using the speedster weapon to stop his mad rampage. Reuniting with Barry, apologizing before Joe and trading banter with Cisco, - all of it influenced Caitlin into leaving her job and coming back to S.T.A.R. Labs. She informed her associates at the bar about her decision to leave and was confronted by Norvock, who tried to strong-arm Caitlin into staying, threatening her for not listening to Amunet's orders. Angered by such an attack, Killer Frost used her meta-human powers to intimidate Norvok, nearly killing him via brain freeze and saying "Touch my hand again and I'll freeze yours off. Maybe some other parts too." Afterward, she was riled up enough to go "have some fun" on a rampage but managed to force herself out of the violent mood, restoring her hair and eyes back to their natural color.

After Cisco finished running Barry through all the new functions of his suit, Caitlin overheard his conversation with Iris and took the opportunity to suggest couples counseling to her which she harshly and rudely declined stating that they would be fine since they're "Barry and Iris" (like that means anything). After their talk, the alarm for an unauthorized breach went off and Iris shouted to Caitlin to come with her and apprehend whoever it was, however, Caitlin turned her back as her eyes began to glow white, signaling Killer Frost attempting to take control. After Iris called her name a final time, her eyes returned to the normal brown and she followed Iris to the speed lab. When they got there, they were aiming weapons at the breach when Wally sped in, they all prepared for an attack until Cisco ran in and told them all to stand down. After many confused glances were sent his way, Gypsy ended up coming through and the three calmed down and exited the lab.

After Barry saves Tim Kwon, whose car had apparently been hacked, the team take the parts of his destroyed car and plug them into a computer only to find that it had the same code as the elevator that killed Kurt Weaver. Caitlin then recognized the code and revealed that it was an organic virus with a digital sub base. Cisco then recognized the names of the victims and him and Caitlin went to start digging into their past.

Caitlin and Cisco were working on finding out how the victims were connected in his lab until Gypsy walked through the door, wondering when she and Cisco were going to go on their date. Cisco then said that he found a picture that could help them in the mystery but couldn't identify one of the people in it. After Barry then saves Joe from a rogue bomb robot in SCIS, the team discovered that the man in the photo was Ramsey Deacon and he had the ability to control any from of technology. Caitlin and Cisco, still in his lab, were still looking for a weakness in Deacon's powers when Gypsy walks in, still wanting to know about her and Cisco's date. He then is forced to cancel their date and Gypsy just lets him know it's fine. Whilst Cisco thinks she is really is okay, Caitlin tells him that it meant she was not okay, he explains that he doesn't get it and she pats him on the back and leaves with a smile on her face after telling him, "You my friend, are in SO much trouble".

Later, after Deacon attacked Sheila Agnani and kidnapped Tim Kwan, Joe, Wally, and Caitlin were looking for both Deacon and Kwan using facial recognition and traffic cams, but to no avail. Iris then asks Cisco, who storms off after thinking about Gypsy, Caitin then goes to talk to him. After trying to calm him down, Gypsy jumps into his lab through a breach and explains that she is fine with him cancelling their date but Cisco remembers everything Caitlin told him and says that when a woman says it's fine, it's not actually fine causing Caitlin to get excited and shout "Amen!". Getting stares from both Cisco and Gypsy, she leaves the room, embarrassed. Later, the team go to the cortex and see a broadcast of Kwan explaining that he and his friends stole the Killg%re project from Deacon. Before Barry goes to defeat Deacon, Caitlin gives him the serum her and Cisco created in order to beat him. After getting his suit hacked and almost being killed, Barry is able to defeat Deacon and he gets incarcerated in Iron Heights.

After the pipes in the West house were making strange sounds, Team Flash spent a day out together where they played a game of laser tag together. After the game, they sat and had lunch just before the breach alert went off and they rushed back to S.T.A.R. Labs. When they reach the building, they find Wally and Harry in the breach room. Harry gives Wally a break-up cube with a message inside from Jesse who wanted to break up him after becoming so busy on Earth-2. After this an alarm goes off, signaling a problem a bank in the city. Before they leave Caitlin angrily tells Harry that they're not done. After Barry fails to stop the newest meta-human threat, Becky Sharpe, Cisco, Caitlin, Harry and Barry all watch the footage in the cortex until Joe and Iris walk in and are able to identify Becky. They come to the conclusion that she is a meta-human with the ability to manipulate luck but don't know how she could have powers since she wasn't in Central City when the particle accelerator exploded. They all begin working in their respective jobs to understand where she obtained her powers.

Later, Barry, Cisco, and Harry come back from looking where Becky got her powers and reveal that Barry coming out of the speed force caused people to become meta-humans. When looking for a plan, Cisco and Harry start to fight and Caitlin attempts to calm Cisco down but he simply states that they don't need him to beat Becky. Barry later tried to talk to her face to face but to no avail as she just caused more people to almost get hurt. He then returned to S.T.A.R. Labs and attempted to come up with a plan with Cisco, Caitlin, Wally and Joe where Cisco ends up naming Becky "Hazard". The rest of the team felt like they had been jinxed and Barry had to talk some sense into them until he gets a call from Iris and leaves. When an alarm sounded in the cortex, everyone ran in and Caitlin explained that there were events caused by bad luck all over the city, which meant that Becky's field of bad luck was growing, they all come to the conclusion that the more good luck she experiences the more her field would grow and the more people suffer. To make matters worse, Becky's field caused the particle accelerator to turn back on. Luckily, Becky ends up suffering bad luck when she didn't win in a casino which caused her field to shrink and Barry managed to get the power-dampening cuffs on her, meanwhile, Cisco and Harry were able to deactivate the accelerator. After everything calmed down, the team managed to figure out that when Barry came out of the speed force, he affected everyone on Central City shuttle 405 and gave them all meta-human abilities. After this, Wally also ends up leaving the team due to his break up with Jesse. Caitlin gives him a hug and tells him "good luck".

After roaming the corridors of S.T.A.R. Labs, Caitlin comes across Breacher and when she reaches the cortex she asks Barry and Joe "why is the scariest person I have ever seen roaming our halls?" and they only respond with "Cisco". They then pull up a photo of Ralph Dibny and explain that he was a former corrupt cop that could've been on the bus on the day of Barry escaping the Speed Force. As Barry leaves, Caitlin and Iris comment on Ralph's handsomeness, comparing him to Oliver Queen. After Joe and Barry pay Dibny a visit, they discover that he is indeed a meta-human from the bus and take him back to S.T.A.R. Labs. When Ralph gets there, his legs are stretched out so far that his foot is in the hallway and as Barry and Caitlin attempt to calm him down, Iris runs in screaming in terror. Whilst attempting to figure out how his powers work, both Harry and Caitlin refer to him as "Silly putty", visibly upsetting him. They all then get into a fight that Caitlin quickly stops when she explains that she needs a sample of Ralph's blood and his arm elacticates, tripping her and making her accidentally throw powder in Ralph's face, causing him to sneeze and his face to fall into his hands, causing Joe to puke.

After calming Ralph down, the team return to the cortex and Iris asks Caitlin if there is anything she could do to help Ralph. She then explains that she would need a DNA sample of Ralph's before he was exposed to dark matter. However, Barry asks why she would help him considering he was a corrupt cop and is still a bad man and Caitlin explained that she took an oath and had to help him. When he refuses to consider that Ralph has changed, Caitlin brings up past events of her becoming Killer Frost. Barry then reluctantly goes to Ralph's office in order to find a sample. He later returns with Ralph's hairbrush, having narrowly escaped a bomb someone had planted in the office. When Barry begins to make remarks about Caitlin becoming buddies with Ralph she explodes with rage on Barry and explains that she understands what it's like to wake up one day with strange powers, which causes Iris to look at them and realize they are arguing like they are a married couple. The two are then interrupted by Joe entering the room but still shoot each other angry glares. Later, Caitlin manages to complete a serum that would help return Ralph to normal and gives it to him. When he drinks it, his limbs return to normal and she explains that he can be any shape he wants to be. He then reaches down to his stomach and reduces his fat into abs.

After Caitlin runs some test on Ralph, Barry and Joe enter the cortex and exclaim that they know Ralph is threatening the mayor with the information that he is cheating on his wife. When Ralph attempts to leave, Barry grabs him and the two begin to fight but when Barry goes in for a punch, his fist goes into Ralph's face. Angry, Ralph leaves the lab, leaving Team Flash shocked. Barry later stops the corrupt Mayor Bellows and reveals his identity to Ralph. The two then return to S.T.A.R. Labs and Barry and Joe reveal to Iris and Caitlin that Cecille is pregnant and all four of them embrace. Later, Caitlin returns to apartment to find a message written on her door by Amunet Black, saying that she misses Caitlin.

Embracing Killer Frost
After receiving the message from Amunet, Caitlin books a flight in order to get out of Central City. Just as she is confirming it on her computer, Iris and Felicity walk in and push Caitlin into attending Iris's bachelorette party. She ultimately agrees but worries that Amunet may find her. Caitlin, Iris, Felicity and Cecille attend the party at a fancy restaurant and Iris notices that Caitlin is drinking excessively. When she looks to the entrance, she witnesses Norvok enter and walk to the girls' table. He asks her to come with him and Felicity mistakens him for a male stripper and when she asks him to take his pants off, he takes out his eye instead. Caitlin flips the table and Iris and Felicity begin attacking Norvok but are ultimately thrown to the ground. When he looks to Caitlin, Killer Frost takes control and the girls are shocked as they watch Caitlin's transformation. Frost then shoots a beam of ice at Norvok, knocking him out of a window and remarking "Ugh! I hate pink" then taking a big sip of the champagne. The three return to S.T.A.R. Labs and Killer Frost retrieves her suit that was stashed hidden from everyone. She then leaves the three other women at the lab and travels to Amunet's nightclub to confront her.

Once she arrives, Amunet is pleased to see her and shows her a meta-human that she has been keeping hostage in order to harvest his powers and sell them as a drug. She then proposes that she and Frost work together to take over the city and become Gods, however, Frost denies this offer and Amunet grows angry and begins to use her powers to slowly raise her metal in a bag beside her. Just as Frost raises her hand, ready to shoot an ice beam, Iris interrupts the two of them and compliments Amunet on her club and then asks Frost to come with her to get out of the club. After considering it, Frost complies and follows Iris out. When they return to the lab, Frost begins to get her things together and tells the girls about Amunet and her history with Caitlin. Just as she is about to leave, Iris manages to convince Frost to stay and fight Amunet instead of run from her. She leaves the lab and meets her under a bridge somewhere in the city and the two begin to fight. Killer Frost shoots at her with two ice beams but Amunet creates a metal shield that deflects both and then launches a large piece of metal into Frost's shoulder. Amunet then picks her up and begins to punch her several times, causing Frost to retreat back into Caitlin's mind and letting Caitlin take all the punches. Two officers pull up next to the scene, which distracts Amunet long enough for Caitlin to escape.

Back in the lab, Caitlin, now back in control, treats her own wounds and is finishing up as Iris walks in to check up on her. She helps Caitlin finish the last stitch on her shoulder and she asks Iris if Killer Frost had hurt anybody. When Iris explained that she didn't, Caitlin regretted coming back to the team and told Iris that she didn't consider her a real friend, only a "work friend" later stating as Killer frost "if you still wanna have a hand for Barry to put a ring on, I suggest you move it". Later, the girls get a location on Amunet and go to confront without Caitlin. However, the plan goes south and she catches Felicity and Iris but before she can kill them Caitlin enters and tries to make a deal with Amunet in exchange for her friend's lives. Her men then point their guns at Caitlin but she screams and sends an ice blast from her mouth at them, knocking them all down and bringing out Killer Frost. The girls get behind her and she creates an igloo around them to take over from Amunet's metal shards. They get the idea to use a magnet to stop Amunet using her powers and Frost explodes her igloo, knocking out all of Amunet's men. As Amunet gets ready to shoot her shards at the three women, Cecille turns the giant magnet on which attracts all of Amunet's shards. Killer Frost then forms an icicle in her hands and prepares to stab her before Iris foolishly stops her and tells her she can choose to be a hero. This gets through to Frost and she drops the icicle but Amunet promises to get her back and escapes, all thanks to Iris. Back at the lab, the boys return from the bachelor party and see Killer Frost standing in the cortex. She transforms back into Caitlin and explains everything about Frost. Later, Caitlin and Iris leave together and Iris asks her to be her maid of honor, which she accepts.

After this, Caitlin accepts Killer Frost as a part of her and the two begin working together as a team.

After Ralph told the team that he received an anonymous tip from some named "DeVoe", Caitlin, Cisco and Harry stayed up all night researching the entire city in order to locate someone with the name. Harry then reveals that he had met new friends who could help them with locating the mysterious "DeVoe". While Harry was contacting them, Barry recommended that they search for the remaining bus meta-humans and asked Ralph to try and identify some of them since he was on the bus. After visiting Dr. Sharon Finkel, Ralph was able to remember a woman wearing a yellow jacket with a bison on the back. A crime scene later showed up and Barry found blood on a statue, causing him to think that the statue may have came to life and so he brought a piece of it to Caitlin. She explains that the statue was flooded with dark matter and it was most likely a bus-meta. Joe then enters the cortex and explains that the victim of the crime scene was transporting an artifact that was formerly in the possession of Kristoff Banks and he then went back to CCPD to put Banks into protective custody.

After Banks is almost killed, the team identify the meta as Mina Chaytan. After Chaytan attacks a truck, Barry and Ralph are able to stop her and successfully incarcerate her but she is later able to escape custody and make her way out of CCPD. She then attacks a museum in order to steal back more ancient artifacts but is stopped by Barry and Ralph and incarcerated again, for good. Later, the team are able to identify and track down the mysterious DeVoe and Caitlin, Cisco and Ralph suit up as Barry and Joe walk up to his home in their civilian attires but when they knock on the door, a wheelchair-bound Clifford DeVoe and his wife, Marlize, answer the door, appearing to be quite normal people.

After Barry and Joe interview DeVoe and his wife, they return to the lab and the team debate whether or not he is the DeVoe they are looking for with Barry assuring everyone that he is the villain. He later manages to steal DeVoe's mug of coffee in order to get DNA for Caitlin to identify him as a meta but she is able to confirm that he is not a meta-human. However, Barry is still convinced that Clifford was the criminal mastermind behind the bus metas, even getting Cisco to vibe his mug but only seeing that he was having dinner with his wife. Whilst the team were sitting in the cortex, Barry walks in and shows them that the samuroid head had a camera in it and is convinced that it is DeVoe watching them. However, they find out he broke into the DeVoe house and believe that Barry has become obsessed with him. Later, Barry reveals that DeVoe knows he's The Flash and that he was right about DeVoe being evil, convincing the team that he needed to be stopped. Cisco even comes up with the name "The Thinker". After the explanation, Wally walks into the cortex and everyone runs to hug him. The team then explain that they are going to wait for him to make a move and get ready for Barry and Iris's wedding.

Stopping a Nazi invasion
Before the wedding, Caitlin, Iris, Felicity and Kara Danvers went together for a manicure and discussed Felicity's relationship with Oliver and his son William. Caitlin remarked that they would be getting married too any day soon and the girls toasted to Barry and Iris. Later that night, before the rehearsal dinner, Caitlin encountered Martin Stein and the two sat down to speak. He commented that the last wedding they both attended together was Caitlin's and even mentioned Ronnie. Caitlin also told him that she helped Cisco and Harry create a serum to separate him and Jax and he told her that he knew since he saw her brilliance in it. She then left to go to the dinner and Martin told her he'd be there soon. At the rehearsal dinner, Caitlin ran into Mick Rory, who had previously kidnapped her back when he was a criminal, and she warned him no to try it again. The next day, the wedding ceremony was attacked by Nazis from Earth-X and the priest was killed by them. During the chaos, Cisco recommended Caitlin introduce Killer Frost, causing her to surface and join in the battle. Frost rose and began firing shots of ice at them, gaining the attention of Mick Rory who helped her. She then created a giant icicle over her hand and stabbed a series of Nazis. After the battle, the heroes return to S.T.A.R. Labs and Caitlin and Martin watched over Cisco who had been incapacitated. When Martin asked why Caitlin was dressed in her suit, she explained how her and her split personality work, which astonished him.

After discovering the Prometheus of Earth-X is Tommy Merlyn's doppelganger, the heroes came together in the Cortex and Harry explained the history of Earth-X, telling them about the Nazis winning WWII and Hitler's only dying in the 1990s. After the meeting, Caitlin and Harry worked together using dimensional vibrations to find the Earth-X Nazis. Caitlin, Harry and Jax attempted to work in Cisco's workshop but knew that dimensional breaching was Cisco's speciality and since he was incapacitated they couldn't find the Nazis. Martin then entered the lab and requested Harry and Caitlin leave so that he could talk to Jax alone, concerning their identity as Firestorm. The team later discovered that Dark Arrow and Overgirl were the doppelgangers of Green Arrow and Supergirl and that the Nazi speedster was Eobard Thawne who had somehow returned again.

Later, Caitlin, Harry and Felicity were attempting to find the Nazis when Caitlin was approached by Mick who asked how she brought Killer Frost to the surface. She explained that Frost appeared whenever she was scared or angry. Mick then humorously shouted "boo" in an attempt to scare Killer Frost out of Caitlin but he was only given an angry glance by everyone in the room. During this, Harry found out how to track down Overgirl and that they should be able to track down her location any minute. After they find the location, Green Arrow, White Canary, Supergirl, Alex, Firestorm and The Flash all go to apprehend the Nazis. However, this turned out to be a distraction to the lure out the heroes so the Nazis could take control of S.T.A.R. Labs. After handing Mick the German Mustard he was craving, Caitlin, Felicity and Iris all hear an alarm go off to alert them of Dark Arrow's arrival. The four went to the Speed lab to hide from him and when he arrived, Mick attacked him head on but Killer Frost came up from behind and managed to grab his bow, beginning to freeze it. However, it sent out a wave of energy that knocked her back against a wall. Black Canary, Wild Dog and Mr. Terrific then began to attack. This was all in vain as all the heroes were locked in the pipeline by the Nazis.

When stuck in the pipeline, Cisco finally woke up and immediately began to argue with Harry. Caitlin gave them a quick warning to stop but they continued anyway. Dinah, annoyed, then asked Caitlin if they were going to be like that the whole time they were trapped and Caitlin replied with a simple "probably".

The rest of the Legends eventually arrived at S.T.A.R. Labs and rescued the heroes trapped in the pipeline. As they entered the speed lab, the group was ambushed by Metallo. However, he was no match for them as Caitlin turned into Killer Frost and all of the combined abilities of Frost, Vibe, Black Canary, Wild Dog, Firestorm, The Ray, Heatwave, Zari Tomaz, Vixen and Steel come together and completely destroy Metallo. During the battle on Earth-X, Stein was injured so Caitlin, Jax and Martin rushed to the med bay on the Waverider in an attempt to save him. Caitlin quickly ordered Gideon to stop his bleeding and after she did, Jax suffered a fit and went into the same state as Martin due to them being linked by the Firestorm matrix. Caitlin suggested that they merge as Jax is the only thing keeping Martin alive. After Caitlin did everything she could, Jax woke up and asked about Martin and Caitlin explained that he was sedated and that she and Gideon were doing everything they could to fix him.

Knowing that Martin's fate was likely sealed, Caitlin left the room and went to talk to Ray. She explained the situation and that Jax was acting as a human life support machine, keeping Stein alive for only so long. Ray remained optimistic that someone on the ship could figure something out. Jax later accepted this and was asked by Martin himself to end it, which he did, killing Martin. Caitlin and Cisco both stared out of the main window of the Waverider as they both mourned Martin's death. Later, Oliver gave a speech about never giving up and stated that they could beat the Nazis, which Killer Frost complimented. Gideon then informed everyone that the Nazis were attempting to contact the heroes. They all stood together as they spoke with Dark Arrow and he demanded Supergirl come with him and they would return to Earth-X quietly. Oliver refused, declaring war and the heroes went out on the battlefield. In order to destroy the Earth-X Waverider, the heroes needed someone on board to self destruct it manually. To do so, Killer Frost, Vixen and Zari all managed to get on board using Frost's ice path. The three managed to self-destruct the ship and escaped through a breach created by Cisco. In the end, the heroes managed to defeat the Nazis and everyone attended Martin's funeral. As Caitlin dropped dirt on his coffin, she asked him to tell Ronnie that she misses him.

Kidnapped by Amunet
During the holidays, Cisco decorated the Cortex with a huge blue Christmas tree and as him and Harry began arguing about the tinsel, Caitlin entered and asked where Gypsie was. He explained that she had to work on the holidays and couldn't make it to Earth-1. When Ralph entered, he mentioned an inside joke he had with Cisco, Harry and Killer Frost, leading Caitlin to believe that her friends would much rather hang out with Frost than with her. She then left to get a coffee at Jitters. At Jitters, Caitlin had a Killer Frost drink as Harry approached her. He told her that even though Ralph may have said that Frost was more fun than Caitlin, Harry thought that she was special and that her friends would much rather hang out with her than Frost. Just as the conversation ended, Amunet burst through the glass doors of Jitters and called out for Caitlin. Harry attempted to hold her off with a gun but she quickly disarmed him and smashed the gun, when she found Caitlin, she tried to turn into Killer Frost but Amunet swiftly grabbed her and put power-dampening cuffs on her.

Amunet took Caitlin to an abandoned hospital building an showed her an injured meta-human she had "found". She explained that she was planning on selling him but he wouldn't come quietly so she was forced to shoot him which ended up with him having a metal shard stuck in the side of his head, ultimately forcing her to seek out Caitlin to help him. Caitlin quickly accepted and explained that she would do what she could considering she wasn't in an ideal environment. When the meta-human woke up, Caitlin introduced herself and he also did, introducing himself as Dominic Lanse. Whilst explaining their situation, Caitlin discovered that he had the ability to read people's minds. Later, when preparing for the surgery, Dominic read Caitlin's mind and asked her about who Killer Frost was, forcing her to explain her alternate personality and how she works. She then questioned if they would ever escape due to her not having her powers at the time, but allowing her to realise that Dominic had powers that could help them.

The two snuck out of the hospital room and used Dominic's telepathy to spot any thugs around corners. However, this quickly failed as they were eventually cornered by Amunet and her men who brought them back to the hospital room. On the way back, Amunet questioned why Caitlin attempted to escape when she hasn't been injured once by Amunet the whole time and Caitlin revealed it was because she was doubting herself. Amunet then revealed that she was once a stewardess, who was constantly hit on by perverted pilots until she obtained her powers and made them pay. She told Caitlin that she was the brightest woman she knew and that she was capable of completing the surgery no matter the circumstances. She then ordered her to get back into the hospital room and complete the surgery.

During the surgery, Caitlin successfully removed the shard of metal and began to stitch Dominic up until he began to go into shock, causing Amunet to move her bag of metal shards, threatening to kill Caitlin. However, it was then revealed that Caitlin and Dominic had devised a plan to escape and managed to lace the ventilation with anaesthetic, knocking out Amunet and her men. The two ran out of the hospital but Amunet managed to catch up to them, almost stabbing them both in the back of their heads. They were almost shot again until Ralph and Cisco arrived and stopped the shards from hitting them, Cisco knocking back Amunet with a vibe blast. The four then escaped through a breach created by Cisco. The next day at S.T.A.R. Labs, the team discuss where DeVoe could be and that he could've potentially drowned after being thrown into water by Barry. That night, they have their annual Christmas party at the West house with even Dominic showing up. However, it is revealed to only Barry that Dominic was actually captured by Amunet and sold to the DeVoes, who killed him and allowed DeVoe to stab his own body and take over Dominic's. DeVoe's body is later left at Barry and Iris' apartment with a knife in his chest, framing Barry for his murder and getting him arrested by the SCIS.

Barry's trial
After Barry was questioned by the SCIS, he was placed on house arrest but was able to attend a meeting in the cortex by Cisco hacking into his ankle monitor. After discussing DeVoe's plan, Barry agreed to go to Iron Heights if he was convicted, not wanting to become a fugitive. The whole team attended Barry's trial at the courthouse and after the lawyer mentioned the knife that was used to stab DeVoe, Caitlin noticed Iris was visibly upset and grabbed her hand. However, Joe got a message about a meta-human attack in the city, forcing him, Caitlin and Cisco to leave Iris with Barry in the courtroom. After studying the medical records of the victims that passed out at Central City Bank at the hospital, Caitlin entered the cortex and explained everything to Cisco and Harry. She told them that they had all suffered from radiation poisoning and that they needed to find the meta-human before he poisoned the whole city or even worse, became a nuclear bomb. Cisco even nicknamed the meta "Fallout".

Later, Cisco and Harry managed to get a location on Fallout and the two went to try and apprehend him while Caitlin stayed and monitored them from the cortex. However, this only turned out to be a waste disposal truck. They finally managed to get a correct location on Fallout and called Barry, forcing him to postpone his conviction. Harry and Cisco then concluded that they needed Killer Frost in order to cool Fallout down and stop the nuclear explosion. At first, Caitlin can't transform because she needed to be scared or angry but after Cisco began listing things that would be destroyed if she didn't fight, Frost finally emerged. After jumping through a breach, Cisco and Killer Frost reached the location and Frost immediately froze Fallout with an ice blast. However, he managed to thaw his way out and shot a beam of radiation at her, sending her flying through a bus sop and knocking her unconscious. Barry and Cisco eventually managed to defeat Fallout and he was incarcerated at A.R.G.U.S.. However, Barry is later convicted and sent to Iron Heights.

Losing Killer Frost
After assaulting S.T.A.R. Labs, killing Matthew, Janet and Edwin; taking their skills and possessing Ralph Dibny, Clifford DeVoe had a confrontation with Vibe, Killer Frost and Flash. When Killer Frost grabbed him to stab him with a block of ice, he used Brainstorms powers to create a psychic block on Killer frost, thereby taking Killer Frost out of Caitlin but not completely taking her from existence.

Caitlin was saddened because she was starting to come to terms, and form a kind of friendship with her other personality. She subsequently tried everything she could think of to try to get her alter-ego back. She concluded that it was possible to get Killer Frost back, she just had to find a way to make her appear.

Trying to recover Killer Frost
After Team Flash defeated Siren-X, the Earth-X doppelgänger of Laurel Lance, Caitlin found out that Killer Frost is alive but without any dark matter in Caitlin's body, she is unable to appear.

The team began to help Caitlin to try and get Killer Frost to reemerge, they ran tests that involved Cisco shooting her with his vibe blasts, which caused nothing to happen. However, while Barry and Cisco are fighting DeVoe, Caitlin appeared and used Leonard Snart's gun on DeVoe in an attempt to get Killer Frost to return, but to no avail as he almost killed Gypsy.

Still desperate to get Killer Frost back, Caitlin finally went to Amunet for help. She led the team to believe that they needed Amunet to help defeat DeVoe and they all managed to get her to help them. Caitlin then struck a deal with her and told her that if she could get Killer Frost back she would do one favor for her. However, it's revealed that Amunet didn't know how to bring her back but still gave Team Flash an item that could help defeat DeVoe.

When Caitlin went to therapy with Dr. Finkel, she revealed that Caitlin had been repressing a memory from her childhood, a memory which was very traumatic for her. She later asked Cisco to vibe her to this memory and see what happened only to see her younger self get hit by a car and then transform into Killer Frost. This revealed that Frost had been inside Caitlin even in her early childhood, before the particle accelerator explosion.

In the final battle against DeVoe, when Cecille went into labor, her powers which she received from her pregnancy kicked in and Killer Frost briefly inhabited her body. She grabbed Caitlin's arm and told her that she had found Thomas and he had been that way all the time.

Searching for her father and recovering Killer Frost
Team Flash had discovered that Caitlin's father's death certificate was a fake and that he was actually alive. Barry, Caitlin and Cisco eventually tracked him down to a warehouse owned by Tannhauser Industries. However, it was later discovered that he was also a cryogenic meta-human that had an evil split personality that attacked the team. The personality wanted to use a serum, that Caitlin reluctantly created, to kill off Thomas for good and inhabit the body himself. Just as he was about to inject himself, Caitlin managed to break through the mental block that DeVoe had created, allowing Killer Frost to emerge and shoot him back with an ice blast. He quickly attempted to convince Frost to take the serum as well and work with him but she refused, stating that Team Flash was her true family. As she walked towards him, she stood on and destroyed the serum. She created an ice-fist and began to punch him but stopped as Thomas' personality emerged and spoke to Caitlin. This turned out to be a short reunion as the evil personality reemerged and shot her back with an ice blast, proceeding to use two ice blasts to launch himself into the air and escape. Later, Caitlin discovered that she could use the cerebral inhibitor to speak to Frost through the mental block and the two began to catch each other up.

During Thanksgiving, Caitlin, Cisco and Sherloque decided not to attend the party at Barry and Iris' apartment, causing Killer Frost to emerge. She questioned they're decision of eating by themselves instead with friends who care about them and proceeded to walk off to the party, asking if they were coming or not.

Battling Cicada
During a battle with Cicada, the entire team was taken down by him, noticing this Caitlin and Sherloque were running ready to shoot Cicada, but not before he threw his dagger full of energy towards them leaving them out of battle, and just as he was prepared to stab Barry with his dagger, Killer Frost emerged and fired an ice beam at him, sending him flying into a nearby van. He quickly stood and escaped the scene. The team later realised that Frost is immune to Cicada's dagger and could be useful in defeating him.

Elseworlds
Killer Frost and Elongated Man were sent to Ivo Laboratories to help deal with A.M.A.Z.O., who had been accidentally activated by an inexperienced Oliver Queen using Barry's speedster abilities. The two and officer Jones were unfortunately not strong enough and as they were floored by the android, it absorbed the two meta-humans' abilities, using Frost's abilities to fly through the roof and escape.

After travelling to Gotham City, Kara Danvers used Caitlin to gain access to Arkham Asylum, convincing the nurse that she was a mentally ill meta-human, even quickly flashing Frost's eyes. After they got inside, a riot began and the two split up. Eventually, Caitlin came across a frantic Nora Fries who was searching for something amongst the shelves. When Caitlin attempted to help her, Nora blasted a beam of cryogenic smoke at her, causing Killer Frost to emerge and engage in a fight. When Nora grabbed her husband's cryo-weapon, Frost asked for some assistance over her comms but before Barry or Oliver could arrive, Nora blasted her back through a table, knocking her unconscious. Upon waking, Caitlin noticed that Oliver and Barry were fighting each other, for what she called help, when Batwoman neutralized them and made them realize that they were exposed to a hallucinogenic gas.

After finding the Book of Destiny, Caitlin and the others began to examine it to find a way to open it, but suddenly the Book disappears in a blue light, leaving Caitlin and company confused.

Altered reality
After John Deegan used the Book of Destiny to rewrite reality and made himself "Superman", Caitlin and Killer Frost's lives were rewritten. It appeared that Frost had fully taken over and worked under Deegan as one of his prime soldiers. After he returned to his base, Frost and John Diggle applauded his actions but he quikcly made them stay quiet and exclaimed that the Trigger Twins had escaped him. Diggle and Frost quickly assured him that they would be captured just as a warning from the pipeline alerted the room. Frost explained that it must have been "Subject 1" but "Superman" quickly explained that he would take care of her himself.

Later, Frost travelled down to the pipeline to speak with Agent Danvers and asked her to go home but became skeptical when she refused. She asked if she had boyfriend trouble but Alex just explained that she thought the work they do is important and she wouldn't change. Frost simply shrugged and left the pipeline. After Kara had managed to get through to Alex, the two attempted to escape Deegan's base but were confront by him, Frost and Diggle. However, a breach opened and Barry, Oliver and the real Superman came through and the two supermen broke through the ceiling and began their fight whilst Diggle and Frost fought Oliver in the elevator. The two were ultimately beaten by him and thrown in the pipeline. This reality was later returned back to normal after Superman used the Book of Destiny to repair it.

Erased future
According to Craig, a member of Savitar's cult, Caitlin would have been described as being "glorious and powerful", and Savitar had "special plans" for her, which did come true as she helped him and he needed her to kill Black Flash.

When Barry visited a possible future, in the year 2397, it is revealed that Caitlin allied herself with Savitar. Moreover, during a climactic battle, Vibe's arms were frozen and shattered by Caitlin, forcing him to replace them with bionic arms and subsequently making him unable to use his powers. Caitlin, still as Killer Frost, has been locked up in Iron Heights, and still refuses to divulge the identity of Savitar, with Julian as her caretaker.

Personality
Caitlin is very intelligent and passionate about her work as a bio-engineer and scientist, even keeping a blood collection kit in her purse. She is generally a very compassionate and caring woman. She loved her fiancé Ronnie Raymond very much, he knew how to make her laugh and was devastated by his death which sent her into a state of depression for almost a year, because of this she didn't smile much. However. since being brought onto the team, working with Barry Allen, helping people and saving lives, she has started to liven back up. She has shown great concern for Barry as she often advises against engaging meta-humans they know little about and was initially against Barry using his powers as a guardian angel for Central City, though she eventually grew to accept and even participate in it.
 * -|As a civilian=

Caitlin is also seen to be somewhat "guarded", in her own words, and timid as seen when she was terrified of going into the S.T.A.R. Labs particle accelerator it being the location of Ronnie's supposed death, though she later overcame this obstacle with Barry's support, becoming more assertive, brave and confident. Despite them being quite different in personality, she is also close friends with Cisco Ramon but finds his need to nickname every meta-human they face annoying, although she has occasionally nicknamed a meta-human now and then herself. Leonard Snart considers Caitlin to be "uptight," which his sister agrees with. When Caitlin was reunited with Ronnie, alive and well after he was separated from Martin Stein, she was overjoyed, no traits of her initial depressive, forlorn personality remaining. When she finally marries Ronnie, she is perfectly content accepting that everything she's experienced over the past year, leading up to wedding the man she loves has been worth it. When Caitlin loses Ronnie again, this time for real, Caitlin is devastated, so much she is unable to stay in S.T.A.R. Labs as she blames herself for his death. However she has slowly managed to recover and regained her desire to help Team Flash.

Though not as prominent as her other traits, Caitlin has a somewhat flirtatious side to her personality. Often when flustered or uninhibited by the effects of alcohol she can become silly, frazzled, and hinted a few times during her night out at the dive bar with Barry that she dropped many hints that she was interested in Barry. After meeting Hunter Zolomon, masquerading under the name "Jay Garrick", he and Caitlin have quickly become infatuated with each other, their infatuation developing into a relationship. Caitlin's love for Hunter was the driving force for her to find a cure for his condition. However, after the revelation of "Jay Garrick" as the man behind the mask of Zoom, Caitlin did not allow her feelings to cloud her judgment on Zoom's misdeeds, rightfully recognizing him as "nothing but a monster" and refusing to accept Hunter's lingering affection for her. Nevertheless, Caitlin called upon those feelings, her face in tears, when she tried to influence Hunter to show his merciful side, sparing Barry Allen from certain death.

After her imprisonment with Hunter, it seems that Caitlin is suffering from post traumatic stress disorder (PTSD), due to her former lover and his frightening behavior and repeated displays of violence in front of her, seeing visions of Zoom when he's not there, and questioning if she still has her sanity.

Since Caitlin has been developing cryogenesis/cryokinesis abilities like her Earth Two counterpart she has been terrified of becoming just like her. While reluctant to tell her friends she has used these powers to aid them occasionally without them knowing, but has gradually realized her inability to control them. This has made Caitlin very terrified but as a result of her changing biology she has become increasingly temperamental, which causes her appearance to become more like her Earth-2 counterpart. However Caitlin is still sane enough to realize this but is only more horrified at her increasingly inability to manage her emotions. However her desire to retain her humanity and her biology changing to make her more "cold", seems to be causing Caitlin to develop dissociative identity disorder.

Worrying about her new-found, uncontrolled powers, Caitlin's emotions become heightened enough that she became a vindictive, angry and cruel individual, similar, but not identical to Frankie Kane's split personality disorder. Also like Frankie, when affected by her powers, her eyes glow pale blue (while Frankie's glow pink). However, while Magenta tried to get rid of the Frankie persona altogether, Killer Frost state amplifies Caitlin's own fears, insecurities and bitterness. As Killer Frost, she mocked Barry by mentioning his most horrible failures including the deaths of his mother, father, Eddie and Ronnie, as well as revealing to Cisco that his brother, Dante was alive in the pre-Flashpoint timeline, before Barry changed it. She expressed bitterness over Barry only caring about himself and his own happy ending, while she was left broken.
 * -|As Killer Frost=

Caitlin also mocked Cisco by calling him pathetic for feeling sorry that he had to hurt her to save Barry. She openly blamed Barry for what's happened to her, yet admitted that she feels broken. She nearly killed Julian and one of Alchemy's Acolytes, however she was still unable to kill Barry, making her snap out of her anger, as she became horrified at what she almost did.

Once Killer Frost was fully awakened due to Caitlin's temporary death and revival, she states that she doesn't want to be cured and wants Caitlin never to come back. She allies herself with Savitar after he reveals himself to her.

Killer Frost went after Tracy Brand after Savitar promised that if she lives up to her name and murders Tracy, she could be a god. She arrived at CCU in her new outfit and attacked Barry and Cisco, but when Barry fought back with fire, she ran away. She then attacked Tracy for the second time outside Jitters and continuously formed an ice slide that she slid on for a while without any difficulty. She took advantage of the fact that Cisco would not hurt her and almost hit him with a blast that Barry took. She stabbed Barry in the leg so that he couldn't follow her and she left, claiming that this is her now.

Later, Killer Frost kidnapped Joe's girlfriend Cecille outside of Joe's home and threatened to kill her if Joe and the team did not hand over Tracy to her and Savitar. Later at the supposed exchange site, she claimed that killing Cecille would bring her no joy but Tracy's death at her hands would. When Barry tried to talk her out of it, she knew exactly what Barry was going to say. She and Cisco later faced off, and while she seemed calm at first, she later fought back as hard as she can and lost to him. Cisco managed to get a sample of her blood, which could be the key to making a cure for her. Before Cisco can take her, Savitar arrived and took her away.

Despite all this, while reluctantly working alongside her former allies, it was shown she still has a strong attachment to her memories of working at S.T.A.R. Labs when she and Cisco reminisced about Ronnie losing his temper back when they were trying to build the particle accelerator. However. Killer Frost also showed in this moment that thinking about who she used to be made her uncomfortable as she quickly, sullenly, stated that she didn't want to stay any longer than she had to. Her conflicted feelings about herself and her old allies was again emphasized when she told Team Flash she never loved them and left, only for the assertion to hurt her heart enough to cause the real Caitlin to emerge for a few seconds once she was out of the team's sight.

Despite her continued allegiance to Savitar, Caitlin began showing signs of regret and doubt in her betrayal. During the final confrontation of Team Flash and Savitar, Cisco's unceasing loyalty for Caitlin finally enabled Caitlin's true-self to become permanently restored and reconciled with her friends. At the same time, she felt lost, unsure of who she is now.

After her experiences with Amunet Black, Caitlin began to realize that she could co-exist with Killer Frost and started treating her alter-ego as a friend and fellow teammate rather than an adversary. Though their relationship was slightly tenuous at first, Caitlin began to develop better control over her powers and accept her alter-ego as a part of her. To which, Caitlin was devastated when her powers were apparently taken away by Clifford DeVoe and determined to find a way to restore Killer Frost.

In the future in which Iris dies, by the time of the year 2397, Caitlin has become too far gone to the point where she refuses to be called real name, as she prefers being called by her alias "Killer Frost", she becomes angry when people call her by her real name, despite her insanity and cold nature, Caitlin is very observant; she was able to realize that the Barry Allen she was speaking to was the younger-self of her Barry; due to the look on his face, as the latter had not yet become emotionally broken, as his Iris was not dead yet. This future was later erased when Savitar killed H.R. instead of Iris.
 * -|Killer Frost of 2397=

Powers
"Persistent subthermal homeostasis with, uh, involuntary gelid substantiation. She gets cold and freezes stuff."

- Kara Danvers


 * Cryogenic/Meta-human physiology: When Caitlin's father, Thomas Snow, learned that his daughter inherited his ALS gene, he used cryogenic research to freeze the progression of the disease, which also granted Caitlin her newfound powers. They remained dormant for 17 years (apart from a few brief episodes during her childhood), as several tests never showed signs of a meta-gene. Three years after the S.T.A.R. Labs particle accelerator explosion, Caitlin's powers finally emerged fully.
 * Accelerated healing factor: While accessing her powers, Caitlin's metabolic rate is augmented to offset cold tissue destruction, allowing her endure more grievous injuries and likewise heal much faster than even a speedster, though foreign matter must first be taken out to not impede the healing. After clinically dying from a combination of a seizure and her reopened impalement wound, she was immediately resuscitated into a stable and cognitive state while her wound seamlessly healed completely in seconds. However, her healing powers only work when her Killer Frost side takes over, as wounds inflicted by Amunet Black left Caitlin bruised and requiring stitches.
 * Superhuman durability: Caitlin has shown remarkable durability, able to withstand multiple punches and cuts from Grace Gibbons, and still keep fighting her without losing consciousness, and was able to quickly get up after being thrown against a wall by Grace's telekinesis.
 * Transformation: After Caitlin and Killer Frost decided to be just one, Caitlin became able to transform into Killer Frost and vice-versa; for example, she remembered her anger against her childhood bully and cut her hand with a broken bottle (which healed immediately) to trigger her alternate personality. Caitlin's transformation affects her physical appearance, as it turns her hair white/grey and changes her eye color to an icy blue.
 * Energy absorption/Cryokinesis: Caitlin's powers work by absorbing all existing heat around her, thereby reducing the temperature and to freeze targets well-below negative 370 degrees, even shattering beings as powerful as the Black Flash. Furthermore, her powers can reach such low levels that they can completely negate a speedster's healing powers and alternatively neutralize accelerated decomposing. Caitlin can create various ice structures with ease, such as large bulletproof shields that can with standing point blank automatic rifle rounds as well as launch upon manifestation sharp projectiles in rapid succession. Caitlin can conjure icy blades around her arms as means of transportation by producing icy waves of such propulsive strength, with one hand behind her, to propel herself forth across an ice slide she forms before her with her other hand, similar to Firestorm's fire-based propulsion ability. Her powers can also affect the weather around her, dropping the climate of the area and cause it to snow. A tell-tale sign of Caitlin accessing her powers is producing icy mist from her hands.
 * Freezing kiss: Caitlin is able to near-instantly freeze people through a kiss, allowing her powers to enter her victims' bodies and freeze them from the inside. This was shown when she kissed and nearly killed Barry Allen before being interrupted by Cisco Ramon.
 * Dark matter manipulation: During her fights with Cicada, Caitlin's powers have shown to be strong enough to briefly negate the powers from his dagger.
 * Cryokinetic constructs: Caitlin can create various structures and weapons made out of ice, of which she can utilize during a fight.
 * Ice spike projection: Caitlin is able to create spikes out of ice in order to use in combat as projectiles, daggers, swords, and claws.
 * Cryokinetic surfing: Caitlin can freeze particles around her, utilizing it to create an ice slide which she can use to get around much faster. She can also use her cryogenic powers to continuously propel her on the slide to increase her speed by placing one hand behind her to push herself along. Caitlin can also extend the slide while propelling herself along by freezing the particles in front of her when she is on the ice slide.
 * Freezing breath: Caitlin is able to create a fog with her breath. About six months following the defeat of Savitar, Caitlin, as Killer Frost, grew powerful enough to orally produce cold mists with enough momentum to knock several people backwards and off their feet.
 * Cold immunity: An added benefit to her powers, Caitlin also exhibits a high resistance to frigid temperatures. She is shown to be able to hold the ice constructs she manifests with little trouble. Caitlin was also seen unaffected by a snowstorm she created after escaping S.T.A.R. Labs and later when Icicle decreased the temperature in a lab to absolute zero.
 * Mental communication: Caitlin and Killer Frost are able to talk to each other whenever one of them is in control.
 * Remote cryokinesis: While transforming into Killer Frost, Caitlin can freeze objects without physical contact to the object itself, as shown when H.R. Wells' coffees had frozen while her presence was near. This ability is seemingly passive, meaning that Killer Frost isn't willingly controlling it. Later on though, Killer Frost isn't shown freezing liquids in her presence.

Abilities

 * Genius-level intellect/Master scientist: Caitlin is extraordinarily intelligent, gaining a PhD and two doctorates by the time she was 28 and being a promising bioengineer at S.T.A.R. Labs. Her talents have been a crucial aid in helping Team Flash. Working together, she and Cisco Ramon were able to use a sample of the Mirakuru to create a cure for it. Caitlin was also able to create new Velocity serums for "Jay Garrick" that temporarily healed him. She also somewhat understands the features of the Speed Force.
 * Computer specialist: As a member of S.T.A.R. Labs, Caitlin has some technological skills of note, albeit not her main area of expertise. This is evident in her ability to reprogram the S.T.A.R. Labs satellite to track meteorological abnormalities over Central City in order to locate Clyde Mardon. Caitlin was able to determine that Ramsey Deacon's powers produced an organic virus and helped Cisco create a compound to invert it.
 * Medical knowledge: Caitlin is an expert in medical care and acts Team Flash's medical support. Caitlin monitored Barry Allen's condition while he was comatose. She was also able to cure him when he was poisoned by Kyle Nimbus and patch him up when he was seriously injured by Tony Woodward, including setting his shoulder back into place. Caitlin was also able to patch up Eobard Thawne after he was brutally beaten up by his Reverse-Flash speed mirage. Caitlin once mentioned that she knows how to perform a lobotomy, a procedure that requires both training and skill in the field of neurosurgery. Caitlin even had the ability to potentially surgically extract a thermite bomb from Lisa Snart's head. Caitlin is well-trained in obstetrics, as shown when she monitored Cecille Horton's pregnancy after the latter gained meta-human powers. Caitlin was even able to successfully deliver Jenna West at S.T.A.R. Labs.
 * Skilled hand-to-hand combatant: To a yet to be elaborated degree, during the six months in which she worked as an enforcer for Amunet Black, Caitlin as Killer Frost developed a measure of sheer hand-to-hand combat skills. She once reversed an arm bar Norvock exerted upon her, slamming and pinning him painfully against a pinball machine. Caitlin also managed to hold her own against and even briefly injure Orlin Dwyer. Caitlin was able to fight on par against an older Grace Gibbons for a while, but was eventually overpowered.
 * Skilled swordswoman: During the Earth-X invasion, Killer Frost was able to create ice swords and take down multiple Nazis with ease.
 * Expert markswoman: Caitlin has incredible proficiency with guns, able to accurately subdue Geomancer by firing the B.O.O.T. at him. Caitlin also displayed excellent accuracy when armed with a Cold Gun, able to incapacitate a riled-up Barry running wildly around S.T.A.R. Labs after he gained enhanced super-speed, something even Cisco was unable to accomplish with his vibrational blasts. After Clifford DeVoe seemingly took away her powers, Caitlin began occasionally the Cold Gun as her primary weapon of choice when operating in the field.
 * Skilled knife wielder: During a fight with Cicada, Killer Frost used a dagger as a weapon, managing to injure him.
 * Indomitable will/High tolerance for pain: Caitlin has a remarkable level of endurance; despite sustaining grievous injuries from an attack by Abra Kadabra, she was able to maintain consciousness throughout her surgery while instructing Julian Albert in removing the shrapnel from her body. Also, after being brutally pummeled into unconsciousness by Amunet, Caitlin was able to recover enough to flee when Amunet was distracted and stitch up her own injuries. Caitlin even eventually overpowered Killer Frost and began coexisting with her alter-ego. During a battle with an older Grace, Caitlin managed to keep fighting despite the former inflicting multiple injuries on Caitlin arms until Grace overpowered her.

Alternate reality abilities

 * Peak of human physical condition: As a henchwomen of Superman, Frost was in top physical condition.
 * Expert hand-to-hand combatant/Martial artist: Frost was a skilled highly hand-to-hand combatant and martial artist; she was able to overpower Oliver Queen with help from John Diggle when he had lost his abilities.

Weaknesses

 * Carbine: Caitlin has implied that like her Earth-2 counterpart, her powers have no effect on carbine.
 * Power-dampening tech: Like most meta-humans, If Caitlin is wearing power-dampening cuffs, she can't use her powers.
 * Abnormally high temperatures (possibly): While never seen, it's possible that Killer Frost can't use her powers under intense heat.
 * "Flashtime": Killer Frost can't use her powers while moving at high speeds since this causes friction between her atoms, which creates intense heat under these circumstances.
 * Nucleokinesis: It is likely that like her counterpart of Earth-2, Caitlin or Frost will be severely affected by nuclear energy.

Former weaknesses

 * Borderline split personality disorder: Caitlin's changing biology also caused physiological effects. The more she would use her powers, the crueler and more sadistic she would become, showing no emotional attachment or regard for human life. While struggling to contain her powers, Caitlin developed a form of dissociative identity disorder which is triggered when angered, making it difficult to calm her down and restore her rationality. The change can be seen as the case of Caitlin's super-powered alter-ego weakening in her psychic apparatus, allowing for her hidden fears, grudges, and insecurities to come to the surface, rather than a true split personality. Over time, her friends continued trust and love for her finally allowed Caitlin to overcome her mental struggles, regaining her sanity while having full control over her powers. However about six months later, having taken Julian Albert's serum to cure her, it proved only temporary and had an additional side-effect of developing a complete separate personality. In addition to the changes happening more suddenly and erratically both ways, it also caused both the Caitlin and Killer Frost side to no longer have any recollection of the other's actions. After some words of inspiring encouragement from Iris West, Caitlin and Killer Frost decided to just be the same person and Caitlin no longer had a problem with her alternate self. Killer Frost eventually started to care about Caitlin and was even concerned for her when faced with the threat of a nuclear explosion.
 * Julian Albert's serum: Julian worked with Caitlin's mother, Carla Tannhauser to create a serum capable of removing Caitlin's powers. According to Caitlin, while the serum initially seemed to work, Killer Frost re-emerged sometime afterwards, stronger than before, and was no longer affected by the serum.
 * Limited/Unstable control of powers: According to her mother, the continuous use of Caitlin's powers would end up making her unable to "turn them off", leading to Caitlin accidentally freezing her desktop monitor. Caitlin seemingly began to use her powers (in small doses) with little to no adverse effect, as shown at Christmas 2389 when she made it snow. A tell-tale sign of her powers overwhelming her are the physical changes she gradually gains from them, such as her hair turning white and lips turning blue. The most noticeable sign of her losing control is her eyes glowing a pale whitish-blue and her distorted voice. The physical changes become more prominent as she makes use of her abilities, though they will recede if she goes long enough without using them, such as her hair going from white back to its original chestnut brown. However, as Killer Frost she is in full control of her powers, to the point where she was able to create a slide of ice to ride across the city. Caitlin is now able to control them through her Killer Frost side, who has become her ally.
 * Mental blockage: While battling Clifford DeVoe/The Thinker after he took over Ralph Dibny's body, DeVoe seemingly used Matthew Kim/Melting Point's powers to take away Caitlin's Killer Frost powers. However, Caitlin later found out that Killer Frost was still inside her without the presence of dark matter in her system; she just needed to find a way to make Killer Frost re-appear. Killer Frost later resurfaced during a battle against her father, Thomas Snow's evil second personality, Icicle, to save her friends. Shortly thereafter, Team Flash realized that DeVoe hadn't used Melting Point's powers against her at all, but instead Dominic Lanse/Brainstorm's powers to place a mental blockage in her mind to keep her from accessing her Killer Frost personality. After discovering this, Caitlin began using the cerebral inhibitor to help herself get back in touch with Killer Frost, although Team Flash suspects that, with time, she should be able to reach Killer Frost again without use of the cerebral inhibitor. After a week Caitlin and Killer Frost is able to talk and switch body's again without the use of the instrument or presence of stress.
 * Emotional state: Caitlin's transformation into Killer Frost is only triggered whenever she is angry or scared, as her split personality requires the surge of heightened adrenaline in her system. However, after Caitlin reunited with Killer Frost following the battle with Icicle bonded with her, she has overcome this weakness and is able to call on her alternate persona whenever needed.

Equipment

 * Killer Frost suit: Caitlin wears a protective suit as her alter-ego, Killer Frost. Upon gaining full control over her powers and aiding her friends in the final battle against Savitar, she stopped wearing it. However, after her Killer Frost side returned, Caitlin starts wearing a new protective jacket when she is in battle.
 * Cerebral inhibitor: Caitlin used the cerebral inhibitor to bypass the mental blockage placed in her mind by DeVoe to talk to Killer Frost. After a week of using the inhibitor, Caitlin and Killer Frost were able to talk and switch body’s without the use of the device. When Nora West-Allen was stuck in Grace Gibbons' mind, and Barry Allen and Iris West were stuck in Nora's, Caitlin used the inhibitor to communicate with them before the device began burning up.

Former equipment

 * Power-dampening cuffs: After her powers began manifesting, due to her unstable control over them, Caitlin initially wore a pair of Cisco's power-dampening cuffs on her wrists as a means to help keep her powers in check. However, she abandoned use of these when she couldn't keep them charged for long periods of time and would have to sit with them plugged in, which she said made her "feel like a human tablet".
 * Solar power collection pendant: Julian made Caitlin a pendant designed to dampen her powers, as well as to collect solar energy in order to help charge it whenever she went outside, so that it continues to work without constant recharging. However, upon her temporary death, Julian removed it; as Killer Frost, she destroyed it.