Vitiate, born “Tenebrae,” was born within the bounds of the Sith Empire sometime before 5,000 BBY, in the Golden Age of the Sith.
After Naga Sadow’s failed attempt to conquer Republic space, Tenebrae tricked many other Sith Lords into coming to his homeworld, Nathema, and conducting a ritual with him that resulted in their own deaths, as well as the draining of all life on the planet.
Tenebrae then absorbed the life essence from the dead, becoming far more powerful. He was reborn as Vitiate.
Vitiate filled the power gap in the Sith Empire left void by their two previous leaders, Marka Ragnos and the ill-fated Naga Sadow, reforming it into his vision, moving the capital from the planet Korriban, the Sith homeworld, to Dromund Kaas, and creating a Dark Council to serve on his whim.
Vitiate manipulated the leader of the Mandalorians, Mandalore the Ultimate, to test and weaken the Republic’s defenses before the Sith Empire revealed itself. While the majority of the Jedi Order remained neutral in the conflict, two idealistic Jedi Knights, Revan and Alek, led a group of Jedi unwilling to let innocents suffer at the hands of the brutal invaders.
Revan brought down Mandalore the Ultimate, and hid his mask, so that there could be no rightful ruler. He sensed that something else was behind this, and, with Alek, traced the trail back to Dromund Kaas, infiltrating the Sith Capitol itself. Vitiate, however, easily repelled the two powerful Jedi Knights, before using the force to corrupt them to the dark side and erase their memory of the encounter.
The pair returned to Republic space, no longer as the heroes Revan and Alek, but as the conquerors Darth Revan and Darth Malak, with armies of Sith Troopers working for them and a powerful relic known as the Star Forge creating new warships by the minute.