The wizard was in a room at the top of a very long ramp that went around and around. He's not far from where you get incense from the snake statue. Hope that helps.
Wyv

I think you are talking about the serpent key/monkey key that you get off Krueg, Wyvern. D wants to know where the skull key is found. If it is the skull key you need it comes from the Serpent Master down a chute somewhere in the maze of lifts after you have done the summoning ceremony and killed the Naga.