The final book in the New York Times bestselling Moonfall series from thriller master James Rollins, a sweeping tale of relentless adventure and survival in a world on the brink of annihilation.

The world is ending.

As earthquakes shatter continents and storms ravage the skies, the moon descends—its burning face growing larger each day. Impact is imminent. Extinction is certain.

Nyx and her allies have one last hope: two colossal engines buried deep within the planet’s core, capable of restoring the world’s spin and casting the moon back into orbit. But such power requires a lost key—one sought by others.

An undying figure of bronze rises to claim it: an ancient enemy of unmatched strength and cunning, determined to turn moonfall into a weapon of total annihilation.

As war engulfs the Crown, Nyx and her companions must fight their way toward the Fist, a deadly volcanic stronghold hidden beyond the Mýr swamps. Here, alliances fracture, wills are broken, and hope fades amid wonders that defy the imagination and horrors that threaten sanity.

Because the truth behind the key is more dangerous than anyone imagined.

To save the world, Nyx must make an impossible choice—one that will decide if she becomes its savior… or its destroyer.

The Moonfall Series:
The Starless Crown
The Cradle of Ice
A Dragon of Black Glass
A Fist of Molten Fire