Soul Hunter is a Night Lords novel written by Aaron Dembski-Bowden and published in March 2010.
FEAR THESE SPACE MARINES
Betrayed, cast from the Emperor's light and hunted as heretics, they are the rebels of the 41st millennium. Garbed in symbols of death, the Night Lords are remorseless hunters and killers. They will never repent for the blasphemies that saw them banished. They prey upon the dying Imperium, bringing death from the darkness between worlds.
AND TERROR IS THEIR MOST POWERFUL WEAPON