The Valdemar Series is a collection of fantasy novels written by author Mercedes Lackey. Set in the fictional world of Valdemar, the series explores themes of magic, friendship, and the struggle between good and evil. The stories often feature characters known as Companions, magical horse-like beings that choose their human partners to protect the realm. The series includes multiple sub-series and standalone novels, with each story contributing to the rich lore of Valdemar. Key elements include the use of magic, the importance of bonds between characters, and the presence of various mythical creatures. The series has garnered a dedicated fanbase since its inception in the late 1980s.