Grey Knights

The Grey Knights are a secret and mysterious Chapter of Space Marines specifically tasked with combating the dangerous Daemonic entities of the Warp and all those mortals who wield the corrupt power of the Chaos Gods. They were created by the Emperor with the aid of Malcador the Sigillite at the time of the Horus Heresy to serve as Humanity's greatest weapon against the threat posed by the existence of Chaos.