Demonica by Megan Derr

Life as a mercenary isn’t kind or easy, and Shale has lost much: one family, then another, one leg, one arm, one eye, and the love of his life when pain and medication left him disinterested in sex. The last thing he wants is to accept a job from his ex-lover’s mother, but the pay is too good to refuse, especially as it should be a relatively simple job.

But crucial information was withheld, and the man they’ve been sent to escort home is like no one Shale has ever met—despite the dangerous reason he’s spent so much of his life sequestered, and the fact he’s part of the family that hurt Shale once before.