Xagyg (sometimes spelled Zagyg) is a legendary wizard who once ruled the Realm of Blackmoor. Rumor is that he was born Zagig Yragerne. Late in his career he was striken ill with insanty thanks to an encounter with a race of beings known as Mindflayers. Afterwards, he built Castle Greyhawk and the Dungeons that lie below it. He is often called “The Mad Architect.”
He is the powerful wizard who was laid to rest in the Tomb of Xagyg.