Zak

Mad Zak is one of the inhabitants of the Abyss colony whose mind broke under the horrible conditions in which he was forced to exist.

When the Avatar found Zak on the third level of the Abyss in Ultima Underworld I, he had developed an almost lethal fear of the darkness and collected light sources like mad to keep the darkness away. At first, Zak wasn't of much use.

Later hower he/she learned that Zak had stolen the Taper of Sacrifice from the Knights of the Crux Ansata. So returning to Zak, he/she offered the hungry man some fish in exchange for the taper, getting the talisman through this deal. The Avatar also tried to get Delanray's candelabra, but Zak didn't any longer have it at that point.

Most likely Garamon rescued him when he teleported everyone out of the doomed colony.