Beneath the towering bleached ribs of a dead, ancient beast lies New Crobuzon, a squalid city where humans, Re-mades, and arcane races live in perpetual fear of Parliament and its brutal militia. The air and rivers are thick with factory pollutants and the strange effluents of alchemy, and the ghettos contain a vast mix of workers, artists, spies, junkies, and whores. In New Crobuzon, the unsavory deal is stranger to none-not even to Isaac, a brilliant scientist with a penchant for Crisis Theory.

Isaac has spent a lifetime quietly carrying out his unique research. But when a half-bird, half-human creature known as the Garuda comes to him from afar, Isaac is faced with challenges he has never before fathomed. Though the Garuda’s request is scientifically daunting, Isaac is sparked by his own curiosity and an uncanny reverence for this curious stranger.

While Isaac’s experiments for the Garuda turn into an obsession, one of his lab specimens demands attention: a brilliantly colored caterpillar that feeds on nothing but a hallucinatory drug and grows larger – and more consuming – by the day. What finally emerges from the silken cocoon will permeate every fiber of New Crobuzon – and not even the Ambassador of Hell will challenge the malignant terror it invokes…

Several years have passed since the demise of Hanish Mein. Corinn Akaran rules with an iron grip on the Known World’s many races. She hones her skills in sorcery by studying The Book of Elenet, and she dotes on her young son, Aaden – Hanish’s child – raising him to be her successor. Mena Akaran, still the warrior princess she became fighting the eagle god Maeben, has been battling the monsters released by the Santoth’s corrupted magic. In her hunt she discovers a creature wholly unexpected, one that awakens emotions in her she has long suppressed. And Dariel Akaran, once a brigand of the Outer Isles, has devoted his labors to rebuilding the ravaged empire brick by brick. Each of the Akaran royals is finding their way in the post-war world. But the queen’s peace is difficult to maintain, and things are about to change.

When the League brings news of upheavals in the Other Lands, Corinn sends Dariel across the Grey Slopes as her emissary. From the moment he sets foot on that distant continent, he finds a chaotic swirl of treachery, ancient grudges, intrigue and exoticism. He comes face to face with the slaves his empire has long sold into bondage. His arrival ignites a firestorm that once more puts the Known World in threat of invasion. A massive invasion. One that dwarfs anything the Akarans have yet faced…