The Grey Griffins series follows the story of four sixth graders who live in the fictional city of Avalon, Minnesota. These four friends formed a secret order named The Order of the Grey Griffins, consisting of, Grayson Maximillian "Max" Sumner III (the leader) and his friends: Natalia Romanov (the marshal), Ernie Tweeny (the steward), and Harley Eisenstein (the warden). In "The Revenge of the Shadow King", the Grey Griffins discover a link between their 'innocent' card game (Round Table) and a magic book (the Codex Spiritus) which Max discovers in his grandmother's attic. The story focuses on the friendship between the four 'Griffins', and their adventures as they stumble upon one dark secret after another and soon learn that the world in which they lived was much more dangerous than they ever believed. With the help of the Knights Templar (a shadowy organization that protects humanity from the monsters and abuses of faerie magic), the Griffins uncover a plot to hand the earth over to the malevolent Shadow King.