To buck the brutal rule of the Republic, Amirzade Sharouk and his men pull off a desperate plan: Destroying the Republic's fleet by joining forces with the legendary sea folk, masters of the leviathans, immense living weapons born of the sea and magic.

Though the gamble succeeds, one of the leviathans vanishes with a valuable human, straining an already tenuous alliance. Her caretaker Nils needs to find her as quickly as possible to redeem himself before his superiors. His search is further burdened by Dastyaf, a furious human warlord and liability in the marine realm. But after combing the deep ocean and discovering the dangers it holds, Nils realizes he may need the human more than he thought, to save his mission and himself.