Guarded By the Hellhound by Marit Prins

Katherine
Somebody’s watching me, threatening me, waiting for me in the shadows. Every day it’s worse, every day I’m more scared and alone. Desperation drives me to the dog shelter. I need a dog— a guard dog. Raider seems like the perfect fit: fierce, strong, protective. But when things escalate, he turns out to be so much more than I thought he was…

Raider
I don’t know who she is; I don’t even know who I am, but all of my instincts scream to protect this female. Her scent, her heat, her essence calls to me. On the inside I’m completely at her mercy, but I ache to hear her beg my name, to bend her to my will until she’s at her breaking point, until she’s utterly and completely mine.
Danger lurks around every corner, and when I find myself back in the pits of hell, there’s nothing I wouldn’t raise to get back to her..

Guarded by the Hellhound is a monster romance with dark elements, containing mature elements, where the Villain is actually the Villain, but the Hero does appear to be a little morally gray – and a HEA is guaranteed.