Zak

Mad Zak the Outcast 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 obsessively collected light sources to keep the darkness at bay. At first, Zak hadn't much to teach the Avatar. Later, the Avatar learned that Zak had stolen the Taper of Sacrifice from the Knights of the Crux Ansata. After returning to Zak, the hungry man agreed to exchange the Taper for some fish. After hearing from Delanrey that Zak had her candelabra, the Avatar told her of having met Zak and where he could be found.

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

Trivia

 * In the Ultima Underworld I Clue Book, Tyball admits that it was him who had implanted this fear of darkness into Zak.