Vitiate

The Sith Emperor was a mysterious Sith ruler who survived the ancient Sith Empire's defeat during the Great Hyprespace War. He fled into the Unknown Regions with his most trusted Dark Lords and began rebuilding the Empire, vowing to return and defeat the Republic. Using dark rituals, the Emperor prolonged his life and his undisputed rule. He led the Sith Empire during the Great War and after its conclusion withdrew, deferring control to his Dark Council, in order to pursue his own mysterious goals.

==Sources= Star Wars: The Old Republic