The Vespertine Treaty by A. D. Wrae

She was the Heir of Life. He was the Architect of Death.

Ophelia Ashworth has only ever known decay. As the last heir of the once-illustrious Life-Touch lineage, her sole inheritance is a family name choked by shame and a magical core cursed by a spreading blight.

In the brutal, elegant world of Aeternia, where Life and Death magic must maintain an unstable cosmic Balance guarded by the Consortium, Ophelia is the most valuable kind of pawn: a beautiful sacrifice.
Her fate is sealed by the ancient Vespertine Treaty, a political decree designed not for love, but for survival. Her purpose: to marry the most dangerous male alive.

Cain Alistair, the Death Heir and the reigning master of the Void, is a creature of terrifying beauty and absolute control. He is encased in cold obsidian armour, haunted by his family’s sins, and utterly devoid of human emotion. He rules his hollow kingdom with surgical precision, viewing Ophelia not as a bride, but as a crucial, fragile asset needed to stabilise his monstrous power and stop himself from descending into madness.

When Ophelia is wrenched from her crumbling home and dragged into the chilling opulence of Cain’s estate, she faces an immediate, impossible choice: surrender to the dark majesty of her captor, or defy the destiny the entire Consortium has orchestrated without thwarting the balance.

In a world where love is a political liability and kindness is a weakness to be exploited, Ophelia must fight a war of psychological survival. For Cain Alistair is more than just her enemy; he is a constant, lethal threat.
He sees her defiance, he craves her light, and he promises to break her down, piece by exquisite piece.
The greatest danger is not the coldness of his touch, but the terrifying truth that her own body is betraying her mind, finding a forbidden fire in his consuming darkness.