The main protagonist Magnus Chase, son of the Vanir god of fertility Frey, narrates the novel in first person. He is a cousin of Annabeth Chase, a main character of the Percy Jackson and the Olympians and The Heroes of Olympus series, who links the two series together. The series consists of a trilogy of books, The Sword of Summer (2015), The Hammer of Thor (2016), and The Ship of the Dead (2017).