Nacht-Mähre

Night Mare is a fantasy novel by American writer Piers Anthony, the sixth book of the Xanth series . In the book, Xanth is under threat of a barbarian invasion from Mundania. Its only hope is the talents of the Magicians of Xanth and an exiled night mare, sent to the world of waking with the dire message: "Beware the Horseman."