The castle of the king was built on Mount Huon. If you are a fan of the Books of Magic series you would recognize Huon as the first king of Faerie and the one who created the pact with Hell. Just one of those connections that sticks with you. I wonder if Neil had any say in the series as editor or did the writer (John Ney Rieber) research that name himself. A wikipedia search lists a french epic poem Huon of Bordeaux and a continuation poem Huon, King of Faerie, so there is a precedent.