Among her earliest works. A classic of the genre, among the first works of Celtic fantasy. Telling a tale of a land where all the sovereigns have land-law -- a mystic link. And everyone knows that the High One is the master of all the land's land-law, and where riddles are bits of historic lore, with reasons appended.
Morgon of Hed, born with three mysterious stars on his forehead, is at home with his brother Eliard and sister Tristan awaiting the merchants. Tristan, describing what she wants, says he can afford it because she knows what he has under his bed, even though it's so dusty that you can barely see the crown.
Which is when they learn that he went to win a riddle game with a ghost, and the price if he failed was death. Given that their parents were recently lost at sea, leaving him Prince of Hed, they are rather annoyed with him. And Deth, the High One's harpist, tells him how King Mathom of An had promised his daughter Raederle to the one who won the crown. Morgon thinks this is so dumb, it could have been anyone -- and then it dawns him that it was him.
He sets out, with Deth. They stop at the city of riddle-masters, where Morgon had studied, and Morgon tracks down Rood, Raederle's brother, to let him know. Rood heckles him about not answering the riddle about the stars on his face. And then they set sail again, but all the sailors vanish off the ship, and Morgon finds himself shipwrecked without a memory or a name. Astrin, who finds him, is a prince who left his brother's court after the brother's marriage; he thinks that the bride was not the woman he had known from childhood, but something else that had taken her place. When they are attacked by mysterious merchants, Astrin kills some and scares off another. This leads to his brother sending forces to bring him and Morgon back to his court and discover more. For one thing, someone identifies one of the dead attackers -- a man who had been dead for two years already.
Morgon sets out to learn answers. It weaves onward in a tale that includes bribing a ghost with its own skull, Raederle's mysterious ancestor who came out of the sea, ghost children who were promised a man of peace, a harp and a sword both of which have the same three stars as Morgon does, learning to turn into a tree, a blinded and crippled harpist, an attempt to find out what happened to Morgon when he appeared to be dead, trying to get ghosts to protect Hed, the return of (some) wizards who had vanished seven hundred years ago, learning to turn into a crow, an army filled with men already dead, a trip through marshes, the reason why their parents' ship was lost at sea, a passionate desire for revenge, a tower you can climb forever, and learning to turn into a vesta, a beast somewhat like a deer. . . among other things.