All That Falls (The Immortal Plane Book 1) by A. N. Horton
"Fae were supremely powerful beings, vessels for the most potent magic. It was why they were the self-appointed guardians of the Immortal Realm. Because they were the only beings powerful enough to keep all the others in check."
Someone is dropping ancient mythical beasts through giant rifts in the fabric of the universe and, somehow, it is Ren Belling's job to stop them.
Living as an abandoned Half Fae in a world that doesn't even know magic exists, Ren finds herself turning to an unlikely ally to heal the mortal realm and save her people. Lark is a banished Fae with a mighty power that he prefers not to talk about even though Ren can see the very glow of it emanating from him at all times.
They strike a deal. He will heal her rift if she will help him back to his side of it. But dangers far worse than the minotaur or the gorgons await them on their journey. Ren knew it from the beginning. Her uncle had always warned her. The Fae are tricky. So what was she thinking?