Following the events of Trollhunters and 3Below, Hisirdoux ” Douxie” Casperan – who has secretly been the apprentice of Merlin for nine centuries – must recruit the Guardians of Arcadia to travel back in time to the 12th-century’s Camelot. During the journey, the heroes learn why the amulet was built, how Morgana became the Pale Lady, and what events lead up to the Battle of Killahead Bridge.