Fall of Angels by Kathryn Ann Kingsley

Asmodeus lied to me.
While I shouldn’t be surprised, to say my feelings for the archdemon are complicated is putting it lightly. But now, I don’t even know if I’ll ever have the chance to decide how I feel about him.
Unfortunately, I know the terrible truth.
Asmodeus told me that I was the only homunculus he made that survived—but there’s another one. The leader of the deadly cult that’s been abducting archangels and archdemons, Octavian, is just like me. He’s a creature made from the flesh of others and given a life he didn’t want.
I’m Octavian’s prisoner now. He’s a sadist and a monster, and I can’t die. That’s a terrible combination. He’s eager to tell me all of what he knows, and why he’s been killing people and taking angels—but it’ll come at a price.
A price I don’t know if I can afford to pay. But I get the feeling I don’t have a choice. I just hope Michael, Azrael, and the others can find me before it’s too late.
I might not be able to die, but there are far worse fates than death.