The Sasaud (Vulcan for "Vanished") were a group formed in Vulcan society in an alternate reality where their homeworld was destroyed at the hands of the Romulan Nero. In this timeline, a number of the planet's inhabitants survived the destruction of Vulcan and sought out a new homeworld for their displaced population. This eventually led to the settlement of the planet called New Vulcan by the mid-23rd century.
However, a number of the survivors were unable to cope with the destruction of their former home in a logical manner but instead experienced intense emotions involving grief and pain that were greater than those seen during Pon farr. Such individuals regressed to a mentality and state seen among Vulcans before the teachings of Surak that brought about the Great Awakening. These Vulcans lived apart from the rest of the civilization on New Vulcan where they lived deep in the wilderness of their new homeworld.
Those members of the Sasaud were considered lost to their kin. In 2260, Spock experienced pon farr and underwent the rite to mate with T'Pring. However, he became consumed with the blood fever and went rogue where he joined with the Sasaud. (TOS comic: "After Darkness, Part 2")