The 'vanished'
The Sasaud are a group of Vulcans that live away from the colony established on New Vulcan. Their name comes from the term meaning 'vanished' in the Vulcan language. After the destruction of Vulcan, not all the survivors could adapt to the loss of their planet in a logical fashion; some were consumed by grief, manifesting as a powerful surge of emotions in the aftermath.
These Vulcans, Sasaud, regressed into a state like that of Vulcans from before when the teachings of Surak were revealed. Abandoning the colony, they could be found living in the wilderness of New Vulcan instead. The Vulcans of the New Vulcan colony considered the Sasaud wholly lost as a result of their regression. The known number of Sasaud at this time was approximately 25.
T'Pring explains the nature of the group to the crew of the USS Enterprise when Spock escapes to join them while suffering Plak Tow in 2260. The Enterprise then beams aboard all the Sasaud, to the brig, and after trying to help them finally decides to beam them back down to the planet after manipulating the ship's transporters to trick the equipment (and the persons being transported) that they are being transported to their destroyed homeplanet of Vulcan. This action cures the Vulcans of their ailment.