Chained Soul by Eva Chase

Who will win the war for my soul?

My return to my mates has brought unexpected joys—and warnings of danger to come. But as we prepare for war with the greatest enemies of the Mists, a new ally arrives with an even more dire revelation.
I haven’t escaped the sadistic Murk king after all. His magic lurks inside me, sinking in its vicious claws. However he can use me to torment the fae I love, he will.
The man who once stood beside him may hold the key to saving all of us. But he and my mates have centuries of hate to overcome. Blood will be shed, lives will be lost… and one of them might be mine.