The Spell Sword is a sword and planet novel by Marion Zimmer Bradley in the Darkover series. The book was co-authored by Paul Edwin Zimmer, Bradley's brother, though he was not credited. The Spell Sword was first published in paperback by DAW in 1974 OCLC 156484864 and has been republished several times.This book is the first in a trilogy within the Darkover series dealing with the evolution of Towers and Keepers.