Abyssium, the mysterious, toxic blue rock mined from the deepest caverns of the Scyllan Sea, can sustain life, power astonishing and impossible machines, and turn men to depraved monsters. Duke Julian of Tyr, one of the three tenuously peaceful nations in the Abyssium zone, has become so addicted to the Abyss that he has fallen deeply into debt to Quenn Jila of Varuna, whose country is rich in resources but plagued with its own troubles.

When Jila refuses to dissolve the rapacious Duke’s debt to her nation, she falls victim to an assassination attempt, which ends in the loss of a heroic young soldier. Fearing more lives may be lost to the Duke’s hunger for Abyss, Jila engages Kai Vale, an Abyssally augmented mercenary with peculiar abilities. In her quest to discover the identity of her Queen’s true adversary, Kai is pursued by monstrous Ducal guards and meets Draven Lockley, Commander of neighbouring Leza’s Imperial Guard. As Leza becomes embroiled in the conflict, mercenary, soldier and sovereign run afoul of a guild of assassins, murderous nobles, fantastic and dangerous Abyssal machines, and a deadly man with no face and an inexorable thirst for the Abyss.