"The Demon Cycle" is a fantasy book series written by Peter V. Brett. The story is set in a world where humanity is threatened by nocturnal creatures called Corelings, which emerge at night to hunt and kill. The series follows various characters as they struggle to survive and find ways to combat these demons, exploring themes of fear, courage, and the fight for survival. The narrative spans multiple books, starting with The Warded Man, and introduces a unique magic system based on protective symbols called wards. As the characters develop and face their fears, they uncover deeper truths about the demons and their own humanity, leading to a climactic battle for the future of their world.