It has been nearly two hundred years since Hadrian Marlowe assaulted the person of the Emperor and walked away from war. From his Empire. His duty. From the will and service of the eldritch being known only as the Quiet. The galaxy lies in the grip of a terrible plague, and worse, the Cielcin have overrun the realms of men. A messenger has come to Jadd, bearing a summons from the Sollan Emperor for the one-time hero. A summons, a pardon, and a plea.

The galaxy remembers Hadrian Marlowe as a hero: the man who burned every last alien Cielcin from the sky. They remember him as a monster: the devil who destroyed a sun, casually annihilating four billion human lives - even the emperor himself - against Imperial orders. But Hadrian was not a hero. He was not a monster. He was not even a soldier. Fleeing his father and a future as a torturer, Hadrian finds himself stranded on a strange, backwater world.

The Tower of Babel is the greatest marvel in the world. Immense as a mountain, the ancient Tower holds unnumbered ringdoms, warring and peaceful, stacked one on the other like the layers of a cake. It is a world of geniuses and tyrants, of airships and steam engines, of unusual animals and mysterious machines. Soon after arriving for his honeymoon at the Tower, the mild-mannered headmaster of a small village school, Thomas Senlin, gets separated from his wife, Marya, in the overwhelming swarm of tourists, residents, and miscreants.

Wily, charming Kuni Garu, a bandit, and stern, fearless Mata Zyndu, the son of a deposed duke, seem like polar opposites. Yet in the uprising against the emperor, the two quickly become the best of friends after a series of adventures fighting against vast conscripted armies, silk-draped airships, and shapeshifting gods.

After more than 500 years of exile, the heir to the empyre is wary about his sudden reassignment to active duty on the Goblin War’s front lines. His mission to rescue an outpost leads to a dead-end canyon deep inside enemy territory, and his suspicion turns to dread when he discovers the stronghold doesn't exist.