Now Magnus faces his most dangerous trial yet. His cousin, Annabeth, recruits her boyfriend, Percy Jackson, to give Magnus some pointers, but will his training be enough? Loki is free from his chains. He's readying Naglfar, the Ship of the Dead, complete with a host of giants and zombies, to sail against the Asgardian gods and begin the final battle of Ragnarok. Magnus and his friends take a boat trip to the farthest borders of Jotunhein and Niflheim in pursuit of Asgard’s greatest threat.