The Serpent Prince of Hades by Riley Knight

Beneath the white city, a song of dread hums.

No one has set foot on Duath Nun’s shores in centuries. Isolated from the world, its people guard a dangerous secret – and protect the entrance to the Empty with their lives.
Seth never meant to fall in love again. Never intended to return home. Failing both, he’s faced with his worst nightmare – a fate worse than death awaits Aethra.
Deep within the capital of Hades, the Acheron stirs, but its guarded by an enemy they cannot defeat. Gods walk the land – and they hunger for the magic Aethra possesses.
Though memories of the past torment him, Seth must pick up their pieces if he wants to save his team. For if he fails to conquer his demons – he’ll lose Aethra forever.

Throne of Glass meets the Infernal Devices in this devastating, swoon-worthy epic romantasy inspired by Greek Mythology.