Castle Roogna

Dec.1985 DEL REY mass market paperback, Piers Anthony (Ghost Writer in the Sky). Millie, a ghost for 800 years wants only one man–Jonathan, and he’s a zombie. To prove himself, Magician Dor volunteers to get the potion that can restore Jonathan to full life. But he has to go back through time to do it, to a peril-haunted, ancient Xanth, where danger lurks at every turn.- Amazon