The Serpent's Shadow recap

With the chaos serpent Apophis loose and the ordered world in peril, Carter and Sadie Kane search for a way to destroy him for good. Their answer is a rare and dangerous magic: to attack Apophis's shadow, the sheut, and unmake it with a spell of execration. To learn the technique they enlist the treacherous ghost-magician Setne, who helps them even as he plots betrayal, and they seek the aid of the god Set, the very enemy from their first adventure. Along the way Walt, dying of an ancestral curse, and Sadie confront what his fate will mean for them. Combining the power of the frail sun god Ra, the gods within them, and the united magicians of the House of Life, the Kanes strike at Apophis's shadow and finally banish the serpent, restoring the balance of Ma'at. The victory comes at a price: the gods withdraw from close contact with mortals, and Walt survives only by merging with the death god Anubis to become his host. Brooklyn House and its training of young magicians go on, and the Kanes sense that other ancient powers are stirring in the world.

Previously: Carter and Sadie Kane, descendants of ancient Egyptian pharaohs, discovered they could host the power of the gods, Carter linked to the war god Horus and Sadie to the magic goddess Isis. In the first book they stopped the chaos god Set from destroying North America and learned that a far greater enemy, the serpent Apophis, loomed behind him; their father became the host of Osiris, lord of the dead, and they founded a school for young magicians at Brooklyn House. In the second book, racing to counter Apophis, they awakened the ancient sun god Ra, though he returned old and feeble, and a sinister magician's schemes helped free the serpent. The Chief Lector of the House of Life died fighting Apophis, and the Kanes' uncle, Amos, became the order's new leader, allying the magicians with the Kanes' path of the gods. As this final book opens, Apophis is loose and gathering power for a last assault on the ordered world.

The Kanes' plan comes down to destroying Apophis's shadow, the sheut, through the forbidden magic of execration, which could unmake even a being of pure chaos. With the reluctant, treacherous help of the ghost Setne and an uneasy alliance with the god Set, they learn to capture and target the serpent's shadow. In the climactic battle they combine the power of the aged sun god Ra, the gods bonded to them, and the magicians of the House of Life united under their uncle Amos, and Carter and Sadie execrate Apophis's shadow, banishing the serpent and saving the world from being swallowed by chaos. The triumph carries a lasting cost: to keep the balance of Ma'at, the gods agree to withdraw from direct contact with mortals and the House of Life, so the close partnership of gods and magicians must end. Walt, whose ancestral curse was killing him, survives by becoming the permanent host of Anubis, the god of the dead, a union that also settles Sadie's divided heart between the two. With Apophis defeated, the Kanes continue running Brooklyn House and training young descendants of the pharaohs. In a closing hint, they become aware of other, non-Egyptian powers stirring in the world, suggesting their story is only one corner of a larger age of returning gods.