Obsidian Hunger by Anna Durand

The darkest magics feed the darkest hunger.

I will raze the Unseen realm and every abomination that lives in it. The obsidian fae abducted and tortured me, murdered my best friend, and ruined my life. After thirteen years of being the crazy girl no one wants around, I’ve finally found a portal to the other world. But I need an elemental to take me through it. The only one who’ll do the job is Max, a sex-starved incubus who wants my body as payment for the service–and my body wants him.

Harper Goode wants to murder me. It just figures my fated mate would turn out to be a mortal bent on destroying my world and me along with it. I might’ve helped save both worlds twice, but I’m no hero. And the hunger won’t let me rest until I’ve claimed Harper. How long can I resist the urge? How long before I become the monster she thinks I am?
We both have enemies hunting us. We both have inner demons to slay. If we don’t kill each other, the dark forces closing in on us just might.