The Riddle-Master of Hed

Blurb

The Riddle-Master of Hed is a fantasy novel by Patricia A. McKillip. It is the first book of the Riddle Master Trilogy, the following two books being Heir of Sea and Fire and Harpist in the Wind. It was published in 1976.
The trilogy makes use of a number of themes from Celtic mythology.
It takes place in a fantasy world divided into a number of countries. Each ruler has a mystical awareness of his or her land: the land-rule. The seldom-seen High One presides over all. Riddles, typically questions about obscure pieces of lore, feature significantly, as does shapeshifting magic.