Witchbane by Lissa Kasey

A power awakening within is tearing him apart.

All Sebastian ever wanted was a place to call home. Bound to Liam, his fated mate, and nestled in the center of a werewolf pack, he’s found one. However, opening portals filled with monsters in his sleep, Sebastian’s power is a wild thing he’s unable to control. And it’s slowly destroying him.
He never asked to be part fae, or for any of their magic. Now something dark is creeping through the pack bonds, bringing unrest and chaos. Desperate to find a safe way to release the churning well of power inside Seb, the pair venture into Underhill, the abandoned land of the fae.
Only Underhill is on the verge of collapsing. It’s a race against time to harness the power of the kitsune and find a way home, or risk being devoured by a dying world.