Trystero, from Ultima Underworld II
Trystero was once a soldier tasked with defending the Tomb of Praecor Loth, but he was killed during a rockslide caused by the Guardian's mages trying to force their way inside the tomb to loot. Due to the circumstances of his death, his grave remained empty, which greatly annoyed the ghost.
Meeting the Avatar in Ultima Underworld II, Tystero talked greatly about the tomb, and then asked if the hero could return his bones to him, describing the place where a jeweled axe should be. The Avatar did him that favor, and Trystero was pleased with the return of his bones. He then warned the Avatar of the dangers deeper in the tomb, including Lethe, Lord Umbria and Morphius. He also told the Avatar that survival in the tomb would be impossible because there was little to eat. Seeing that his new friend nonetheless wanted to press on, he wished the Avatar luck.
Later, Praecor Loth finally left the world to rest, so Trystero's soul escaped to the void, finally at peace.