Nocturnal Magic — C.N. Crawford

"Remember the darkness. Only the darkness will save you." As part of a deal with the god of night, Ursula is sent to the Shadow Realm. There, she must live in the forbidding palace of an ancient night demon. Granted--he seems to hate her. But he's easy on the eyes, powerful as hell, and he's supposed to keep her safe. But all that changes when the god of night chooses Ursula to fight for him in series of trials. Now, she must vanquish a horde of lethal demons, one at a time. Worse--she may have to battle her own guardian, who has centuries of slaughter on his side. And only one can survive. In order to live, Ursula must learn to fight like a brutal shadow demon, and resist the dark temptations of the realm. If she fails, the god of night will drag her down into hell with him.