The Flying Sorcerers — David Gerrold; Larry Niven

SHOOGAR
was the greatest wizard the villagers had ever known. His spells could strike terror in the hearts of even his most powerful enemies. .

THE STRANGER
had come from nowhere, but his magic was as strong as any that Shoogar or his flock had ever seen--and, to make matters worse, he possessed a most amazing flying spell. .

THE SHOWDOWN WAS INEVITABLE
There was no room in Shoogar's world for an intruder whose powers matched his own, let alone one whose powers could excel his So before the blue sun could cross the face of the red sun once more, Shoogar would show this stranger just who was boss!