The Magpie Lord — KJ Charles

Lucien Vaudrey never planned to return to England. But with the mysterious deaths of his father and brother, it seems the new Lord Crane has inherited an earldom and his family's enemies.

Magician Stephen Day has good reason to hate Crane's family. Unfortunately, it's his job to deal with supernatural threats. Besides, the earl is unlike any aristocrat he's ever met, with the tattoos, the attitude... and the way Crane seems determined to get him into bed.

Evil pervades Crane's house, a web of plots is closing round them, and if Stephen can't find a way through it—they're both going to die.

I'm re-reading this because it's one of my favorite historical paranormal m/m romances ever. Highly recommend!