Darkest Night by Alessa Thorn

It started with seduction and ended in theft.
Rivals. Enemies. Lovers.
All is fair when the price is this high.
Tomb Raider meets Mr and Mrs Smith in this fast-paced romance that’s full of action, steam, magic and revenge.
Three years ago, Kon seduced a mysterious woman and stole a magical artifact from her. He thought their paths would never cross again. He had just made the biggest mistake of his life.
Found as a bloody child in a forest, and raised by one of the most ruthless and calculating mercenaries dirty money can buy, Athena Edgeworth isn’t the kind of person you betray and get to walk away unscathed.
It was the perfect rivalry waiting to happen.
Both know they should end their dangerous game once and for all, but they are addicted to the thrill of the chase…and to each other.
When they get a common enemy hunting them, they will have to put their vicious rivalry aside and work together.
Kon’s only ever wanted revenge, but Athena Edgeworth’s dark heart might be the prize he’s always been searching for. And she’s not about to let him have it without a fight.