The Testament of Yaru Korsin was delivered by Grand Lord Yaru Korsin prior to his death in 4975 BBY. This Testament was a recording stored in a holocron and was read every twenty-five years at Testament Day until 3000 BBY. The Testament identified his daughter Nida Korsin as his successor, outlined the structure of the Lost Tribe of Sith, condoned the killings of the spouses of deceased Grand Lords, and ordered the banishment of his estranged wife Seelah Korsin. It was recorded over an earlier recording in which the Sith Lord Naga Sadow ordered Yaru to transport his brother Devore Korsin and his mining crew to Phaegon III.
In 3000 BBY, the original recording of the Testament was lost after Iliana Merko, the leader of the Sisters of Seelah, destroyed the holocron storing it. However, the Caretaker Varner Hilts had memorized the text. In addition, copies of Korsin's Testament survived in the libraries of the towns of Orreg and Elvarnos. In 2975 BBY, it was subsequently replaced by the Testament of Varner Hilts during the Hilts Restoration as the main manifesto and legal document which guided the Lost Tribe.
The Testament began with a statement by Yaru Korsin that when the ancestors of the Lost Tribe first landed on Kesh, they had been few. Since their survival was not guaranteed, the Tribe had been created as a mechanism mechanism to guarantee the Tribe's survival. After subduing Kesh, the Tribe's founder warned that the only threat to the Tribe came from within itself. Grand Lord Korsin also told his daughter and successor Nida Korsin that the "true power" was behind the throne and that should disaster befall, the Tribe should remember that. Korsin also outlined the Tribe's hierarchy and how the structure should be managed to prevent uprisings like the one that ultimately killed him. In addition, the Tribe's founded also advocated killing the spouses of deceased Grand Lords and banishing his estranged wife Seelah Korsin, who had engineered an attempted coup d'état with the intention of overthrowing Korsin and installing her own son Jariad Korsin as Grand Lord.
Yaru Korsin also advised his listeners to promote their own people to the positions of Sith Lords and High Lords in the Circle of Lords, the Tribe's governing council. This was followed by several minutes of tedious logistical details detailing the Tribe's structure. Finally, Korsin concluded with a statement telling his daughter Nida that she was the only "good thing" to come from Seelah. He also designated her as being responsible for the Tribe's future on Kesh. While it had not been the Tribe's choice to live on Kesh, Korsin argued that they had a choice not to die there. That choice had to be made by his descendants. Shortly later, Korsin died and the transmission stopped.
- Lost Tribe of the Sith: Savior (First mentioned)
- Lost Tribe of the Sith: Pantheon (First appearance)