Harpy (Coven Book 1) by David Neth

Saving him is their job, but it won’t get his victim justice. Samantha and Kathy are witches who protect the nonmagical from evil. So when they spot a coven of harpies targeting Mark, a nonmagical man, they immediately rush to save him. With the threat of the harpies still looming over Mark, the sisters learn more about him and the target on his back. Namely, that the harpies are hunting him to drag him to hell to pay for his crimes against a young woman. However, that presents a dilemma for Samantha and Kathy: do they follow their duties as witches and save the man who harmed a young woman or do they step aside and let the harpies drag him to hell to pay for those crimes? The clock is ticking and the longer it takes Samantha and Kathy to decide what to do, the more innocent people that will be hurt by the harpies while they wait to sink their claws into Mark. Harpy is the first book in the Coven series, which serves as a prequel series to the Under the Moon series.