Elseworlds (concept)

Elseworlds are a multiversal phenomenon masterminded by Mar Novu, the Monitor, to test denizens of various Earths. According to Barry Allen of Earth-90, the Elseworlds are created to approximate the events of an upcoming crisis that the Monitor anticipates: the collision of realities.

Overview
Elseworlds is a unique multiversal concept unlike the ordered parallel universes that form the multiverse together, and more akin to something like the Fifth Dimension, or the alternate worlds one can travel to using the Egyptian dream temple technique. They are based around reality warping, similar to what can be achieved via timeline fluctuations, like the "mirage timeline" of the Flashpoint, or the more direct alteration of reality with the use of the Spear of Destiny, such as Legion of Doom's alternate reality. Much like timeline alterations, Elseworlds usually concern only one universe they are based on, and Elseworlds-based changes are not registered in the memories by denizens of other universes.

Elseworlds are based on existing universes (like Earth-1 and Earth-90), rewritten to a certain point by the Book of Destiny. The alterations might be relatively minor, like swapping Oliver Queen and Barry Allen's destinies, or making John Deegan's dreams come true, or they can be fundamental, like making Barry and Oliver into fugitives (the villainous "Trigger Twins"), pursued by SCIS officers Malcolm Merlyn, Joe Wilson and Ricardo Diaz, along with Superman in a black suit. These warped variations of universes represent Mar Novu's vision of a coming multiversal crisis based on the collision of realities, which is why he intends to test the heroes of various universes by thrusting them into such warped worlds and making them figure out ways to save their realities.

Elseworlds' versions of universes created by the Book of Destiny are characterized by red skies and immense red lightning following the objects of reality warping. As a result, when the destiny-swapped Barry Allen and Oliver Queen moved from Central City to Star City, the lightning storm followed them.

History
According to Barry Allen of Earth-90, the Elseworlds were created on various universes by the Monitor, using the Book of Destiny, including Earth-90, which led to this universe's demise. The Monitor, however, considered the death of those universes a failure on behalf of their heroes, and a test for the coming crisis.

Earth-1's Elseworlds event first came from the Monitor asking John Deegan to take on the mantle of a god and warp the world according to his dreams of power for all people, not just certain unique "supermen and superwomen". This resulted in a number of changes, most prominently swapping Barry Allen's and Oliver Queen's destinies, including their names, powers and abilities, and people's cognition of the two, leaving only the two men with any memories of their previous lives. However, denizens of other Earths, such as Earth-38, would retain their memories of the old state of this universe. Additionally, people's memories of certain events concerning their history was also changed (such as Oliver Queen being released from Slabside Maximum Security Prison with the help of SCIS, without Felicity Smoak's knowledge). With the help of Supergirl and Superman, Oliver and Barry managed to take a hold of their new abilities and returned to their universe, taking care of dangers to their cities, such as A.M.A.Z.O. and various crimes. Cisco Ramon managed to vibe John Deegan's conversation with the Monitor, and showed his vision to Oliver and Barry, allowing Oliver to recognize the general area as Gotham and speed-sketch the portraits of Deegan and Novu.

Assisted by Kate Kane, the superheroes figured out the link between Deegan and the discrepancies in the timeline, especially after their suspicions were confirmed by Barry Allen managing to send a message through the multiverse, notifying A.R.G.U.S. that the Book of Destiny was the key to Elseworlds. Although Deegan slipped away, Supergirl managed to take the Book of Destiny with her. Afterwards, Barry Allen from Earth-90 appeared before the heroes in flesh and explained the Elseworlds phenomenon, just as Mar Novu appeared on the news. He congratulated the heroes on their first successes in finding the book, but immediately teleported it back to his hands and sent Allen away to an unknown destination. He then teleported to John Deegan and gave him the book once again, asking to think big, beyond mere dreams, and thus to make more drastic changes to reality. This resulted in a new Elseworlds version of Earth-1, with Barry and Oliver as the villainous "Trigger Twins", pursued by a Superman in a black suit and their old enemies, now working as SCIS officers.