The Ri-gla-yehat was a Vulcan term that meant the "Unseen" and referred to those members of the race that left the homeworld settlement of Kren'than. This was typically seen as many Vulcans decided not to remain in the commune and instead leave their village. Some, however, were noted to return as the commune never turned anyone away. When requesting entry to rejoin the community, the village elders proclaimed them "ri-gla-yehat" where they served as a probationary period where they were never approached or addressed by any other members of the settlement; as if they did not even exist. This probation lasted to the Terran equivalent of twelve years.
It was believed that the reason for the long probationary period was for the returned Vulcan to demonstrate that they had a renewed commitment to the communes way of life. Thus, it represented that the individual had cleansed both their body and their mind of any remnants of the society that they initially chose to embrace at the expense of the commune. (VAN novel: Open Secrets)