#SithSunday: Darth Nihilus, the Lord of Hunger. He was a villain in KOTOR II and his story is a tragic and eerie one. He was described as a "wound in the Force."
He was a part of Darth Traya's Sith Triumvirate alongside Darth Sion. He encased his spirit within his mask and armor to stay "alive." He survived by feeding on the life force of all living things.
Of course, the good guys always prevail and Meetra Surik, the protagonist from the game, destroyed his life force, as well as killing Traya and Sion as well.