Feehan, Christine - Dark Guardian (Dark Series #9)

Dark Guardian (Dark Series #9) by Christine Fehhan

From the Publisher:

After centuries of soulless existence as the dark guardian of his people, Lucian suddenly craves lady cop Jaxon Montgomery. Jaxx would sacrifice anything to shield others, particularly since a deadly menace dogs her every step. Oddly, Lucian, a born predator who ran with the wolves, vows to guard her for all time.