Havemercy (Havemercy)

When their enemies, the Ke-Han, come up with a scheme to conquer Volstov, a country protected by magicians, metal dragons, and an unlikely quartet of heroes who ride them--exiled magician Margrave Royston, country boy Hal, unpredictable airman Rook, and Thom, a grad student--band together to save the kingdom. Reprint.