The Forbidden Tower is a fantasy novel by Marion Zimmer Bradley in her Darkover series. It was originally published by DAW Books (No. 256) in 1977. It is the sequel to The Spell Sword and is followed by The Bloody Sun. The major characters also appear in Thendara House and City of Sorcery.This book is set approximately forty years after the events in the book Rediscovery. The Hilary Castamir stories in Marion Zimmer Bradley's Darkover precede The Forbidden Tower by about ten years.