Silanus, from Ultima Underworld II
Silanus was at the very battle where Praecor Loth found his death, and even observed Lethe in action, believing her to be more monster than human. Years later, many of the Guardian's agents had failed to retrieve the Horn of Praecor Loth from the grave, so Silanus volunteered to win the Guardian's favor. He thought that being well prepared would enable him to make it. He got all the needed potions, a vest that protected him magically from fire (Leather Vest of Flameproof), and a special key which the Guardian said would enable him to bypass the Three.
While Silanus did manage to reach the third level, he had underestimated the traps. After getting poisoned by a Skeleton's sword, he drank a cure potion only to die of poisoning. Morphius had installed traps that turned any cure potion into pure poison. His spirit was held in the tomb by The Three's magic.
Many years later, the Avatar encountered him in Ultima Underworld II. Silanus' bond to the Guardian had long been cut by his death, so he didn't feel any enmity towards the Avatar. Instead, after telling his story and the importance of the Horn, he went on to describe the dangers ahead, and welcomed the Avatar to retrieve his equipment, describing how to get the special key.
When Praecor Loth later finally left the world, Silanus's soul could finally escape to the void.