The History of the Runestaff consists of
The Chronicles of Castle Brass
Two stories by other writers featuring Hawkmoon have been written
The first is an episode between The Runestaff and Count Brass, the second has Hawkmoon as a young man meeting Urlik Skarsol.
Hawkmoon also appears in the Elric novel The Sailor on the Seas of Fate, part of which is a section of The Quest for Tanelorn told from Elric's point of view. An alternate Hawkmoon, perhaps from a different cycle, appears in The White Wolf's Son.