Bound By Shadow

Falling for a demon can be hazardous to your heart.

Riana Dumain is a fully trained Sybil, a warrior priestess battling evil whose practical magic keeps her grounded in earthly science -- and desires. She knows that gorgeous NYPD detective Creed Lowell is dangerous, and possibly a foot soldier of the evil Legion cult, using his badge and drop-dead looks to consolidate demonic power.

Creed's low-profile Occult Crimes Unit pulls Riana and her two sister Sybils into the case of a politician's son, murdered in a ritualistic sacrifice. Soon, Riana's instincts prove true. Creed, the hottest half-human she's ever known, a demon in bed and out, is guarding a trapdoor to hell. And unless Riana can find a way to tame her mystery man's treacherous inner self (and her heart), all of Manhattan may be enveloped by darkness.

This is #1 in Dark Crescent Sisterhood Series.