"Heralds of Valdemar" is a fantasy book series written by Mercedes Lackey. The series is set in the fictional land of Valdemar, where magic and mythical creatures exist. It follows the adventures of young individuals known as Heralds, who are chosen by magical companions called Companions to protect the realm and uphold justice. The series explores themes of friendship, loyalty, and the struggle between good and evil. Each book features different protagonists and storylines, but they are all interconnected within the rich lore of Valdemar. The series has gained a dedicated fanbase and is known for its strong character development and engaging plots.