Zoranthus, from Ultima Underworld II
Zoranthus became disgusted with what the Guardian had done to his world, thus wanted to find ways to battle the evil megalomaniac. Retreating into the deeper levels of the Pits of Carnage, where the Guardian was unlikely to look, he started researching other worlds. Zoranthus learned much about the Guardian's empire and the mechanics of travel between worlds. He also devoted his time to studying air djinn, and even managed to catch one in a special djinn bottle.
After finding Zoranthus in the lower levels, the mage recognised a fellow enemy of the Guardian and spoke about his world's past, how the Guardian had taken away all the honor and laws in their world, so that it had descended into barbarism, creating an endless supply of soldiers for his army. He also explained the workings of travel between worlds, and revealed that even the Guardian's resources were limited and already stretched thin.
When the Avatar asked for the djinn bottle, Zoranthus offered a deal. He would exchange the bottle for the Scepter of Deadly Seeker. After he later received the scepter, he gave the Avatar the bottle together with explicit instructions on how to capture the air djinn within a body.