Trisch, from Ultima Underworld
She told the Avatar how she'd been responsible for the Taper of Sacrifice, until one day the mad Zak came and stole it from them in his insanity. She had no idea where he was now, as they'd lost sight of him before they could give chase. The Avatar however knew, and got the Taper back from Zak on the third level.
Trisch was very happy to see it again, but told the Avatar to keep it, since the hero had earned being its new keeper by reclaiming it. She also explained how the Taper worked and that it is an infinite lightsource.