Inventive trials and supporting characters boost this otherwise standard-issue quest fantasy. Middle-schooler Jason falls through a zoo hippo’s mouth into Lyrian, a land ruled by a wizard named Maldor, whose only weakness is a magical Word that will unmake him. Each of that Word’s six syllables are hidden behind different defenses, and Jason and sidekick Rachel—a lost Beyonder like him, who proves to be just as intrepid and at least as pig-stubborn—face a series of trials. There is a lake in which anything that stops moving for even an instant gets sucked down, a tree (in the middle of a swamp well-stocked with giant carnivorous toads) that robs interlopers of their short-term memories, a deadly political battle waged with riddles and other tests. Along with such allies as a gent who can detach and reattach any of his body parts (including his head) at will and a warrior who gets to start over as a 20-year-old any time he’s killed, Mull provides his young protagonists with a foe as genuinely clever as he is powerful and rescues an ambling plot with a devastating climactic twist. Readers fond of fantasies that don’t take themselves too seriously will enjoy this trilogy opener. (Fantasy. 10-13)