Darth Mortilus

Darth Mortilus was a Sith Lord born over 200 years before the Great Galactic War.

History
Not much is known of Mortilus' early history, except that he was born within the Sith Empire shortly after the time of Darth Revan.

As a Sith, Mortilus experienced an accident that left him in a mindless, ghost-like state for more than 200 years. When Mortilus finally awoke, all he had known was long gone.

He knew the Sith that later prophesied about the Galaxy's destruction at the hands of the Sorcerers of Rhand, unless the Jedi and Sith united. He witnessed the Sith warrior's descent into madness and saw the Sith kill three hundred Sith on Ziost before a blow was even landed on him. It required an orbital strike to finally defeat the crazed prophet of doom.

At some point, Mortilus created a holocron with his teachings, a sample of dust, and components of his special lightsaber within.

Mortilus was then sealed in carbonite with 1,000 Sith troopers on a rocky planet as a fallback plan for the war. He was released three and a half millennia later by an unnamed Sun Guard and future Sith.