Darth Vilus was a Sith Lord of the resurgent Sith Empire, who was dead before the Cold War, who produced over three thousands volumes of writings. He had several apprentices, the fourth of whom he killed after catching him spying. After using the ritual of Force walk, he began hearing voices of the bound Force ghosts in his head and set out to find a cure. He discovered a forbidden Ritual on Voss that could heal fractured minds and he kept writings of this technique. Unfortunately, before Vilus could confirm this discovery, he went insane.
Years later Sith Lord Kallig, who suffered a similar problem, discovered the writings of Darth Vilus in Darth Thanaton's private library and traveled to Voss, where they successfully performed a ritual, establishing control over the ghosts in their head.
- Star Wars: The Old Republic (First mentioned)