Sabat 6

The sixth book in the Sabat series.
Mark Sabat, ex-priest, SAS-trained killer, exorcist, had been a man with a dreadful mission for most of his life. His evil brother, Quentin, had chosen the Left Hand Path and his soul had haunted Mark.
Finally, Quentin had been destroyed but now Mark faces another enemy, master criminal The Reaper who is also one of Satan's disciples. The Reaper, following his escape from prison, is bent on revenge on G. N. Strong, the private detective who had been instrumental in his capture.
Sabat's role is to protect Strong from a deadly foe who has supernatural powers.
His enemy is the eternal principle of evil made flesh.