The Wizard of Yendor (also informally known as Rodney) is the guardian of the Book of the Dead. He resides in his tower in Gehennom. You must get the Book of the Dead from him before you can descend to Moloch's Sanctum and get the Amulet of Yendor from the high priest of Moloch. Rodney is generated without a weapon. The wizard can and will follow you up to the Elemental Planes. However, he will not appear in the Astral Plane, though if he appears on the Plane of Water, he can follow you through the portal to the Astral Plane.