Soul Wardens (The Artificer Book 4) by Marcus Cass

A new commission becomes an unexpected and dangerous challenge. This time I’m dealing with the denizens of the Shadow World—thieves of human souls. My search for answers takes me to a small northern village whose secrets are guarded not only by people, but also by monsters. To prevail, I must master the powers of both Light and Shadow. As if that weren’t enough, my fluffy pets reveal a surprise. A big fat magical surprise. But I’ve handled worse—I’m an artificer, after all. So I’ll figure it out.