Rough Justice by Kelley Armstrong

Mallt-y-Nos. Matilda of the Hunt. The lone woman who rides with the Wild Hunt, tasked with finding killers who’ve escaped justice and letting the hounds reap their souls. For Olivia Taylor-Jones, Matilda isn’t just a legendary figure from Welsh lore. She is Olivia’s past, and her future, one she’s finally embraced.

Having accepted her role as Matilda, Olivia must now lead her first Hunt. Seems simple enough. But when she questions their target’s guilt, the Hunt is halted, her mission failed. Still, it’s just a matter of getting Gabriel’s help and investigating the man’s past to reassure herself that he’s guilty. He must be. Otherwise, he wouldn’t be a target. But the deeper she digs, the more problems she finds, until she must question everything she knows about the Hunt and the choice she’s made.