These design sketches of mine of The Horned King for The Black Cauldron are currently being offered at Heritage Auctions. They come from the collection of producer Joe Hale.
Black felt pen and Magic Markers, early 1980s.
I have always enjoyed working at this stage in production. Just imagining character concepts inspired by the story material. The movie was based on The Chronicles of Prydain books by Lloyd Alexander, and they are wonderful. With today's technology The Black Cauldron would make heck of a live action film.