In a world being erased by a creeping, cosmic rot called The Null, Lily Carr is a living contradiction. Born of a forbidden union between warring kingdoms of light and shadow, her very existence is a crime. She is the Anathema, an outcast wielding a power so volatile it threatens to tear her apart-a power that might be the world's only salvation.

When a desperate king, hunted by both the blight and a usurper to his throne, summons her as his last resort, Lily is thrust into an impossible quest. They must unite two ancient, opposing artifacts: one from the heart of a sun-drenched enemy city, the other from the deepest, most haunted tomb of her own people. Guided by an enigmatic thief whose secrets are as dangerous as the monsters they hunt, they are pursued by fanatics, haunted by betrayal, and shadowed by the terrifying truth that their only hope might be a world-ending lie.

As a fragile alliance blossoms into a forbidden romance, Lily and the outcast king discover that the cost of mending their dying world may be her very soul. To save everyone, she must harness the catastrophic power that wars within her-a power that could either become the world's ultimate weapon, or its final, glorious doom.