Fated Despair by Tessa Cole

There’s no outrunning fate once it’s branded her heart.
I’d thought I was safe, free of the horrible fate awaiting me. I’d never been more wrong.
Now I’m living in my worst nightmare. I failed my guys as we fought for our lives against the Shadow King and his assassins, and the mating brand I’d tried so hard to get rid of flared to life.
Only one thing can break its agonizing power without killing me. Faerie’s Heart.
But we have no time to succumb to crushing heartbreak and sorrow. Somehow, we must pull our drained powers and broken bodies together — and evade the Winter Queen’s assassins — to find the final key needed to release the Heart before the Shadow King can get his hands on it. Failure means he will control all of Faerie.
And the brand will become a chasm — putting my guys and their love forever beyond my reach.