Death Bringer by Kate Pearce

A powerful magic user is stealing people’s faces in San Francisco, and empath Ella Walsh and shifter Vadim Morosov have been called in to investigate. Still adjusting to the closeness and permanence of their new relationship, the government-paired mates are soon hot on the trail of an Otherworld cultist from Vadim’s past.
But their target turns the tables, and after he gives Ella someone else’s face, the couple will have to follow him to Otherworld to get hers back. There, in an ancient world of family ties, old grudges and monsters, where living memory stretches centuries, Ella will have to confront the dangerous truth of Vadim’s bygone life.
Because there’s a reason the Fae call him Death Bringer, and if Ella can’t unravel it, she may never see her mate—or her face—again.