Vargr by Cari Silverwood

Cyn falls from the top floor of the world into the arms of Vargr, a beaster who rates a diamond 10 on the Scale of Hardness. In her hands is a piece of Ghoul Lord.
She’s forgotten the last five years of her life, the years of the invasion of the Ghoul Lords.
The beast horde was meant to save Earth. Once human, they now carry gene-warping nanomachines in their blood. No one told them they’d also been injected with the remnants of myths and legends.
They tried and they failed. What can Cyn with her amnesia and sparkly eyes possibly do? Vargr isn’t sure, but he’s beginning to see the pros of nailing a naked Cyn to the wall and floor, over and over, until he gets some good answers.