The Grey Knights Models are a secret chapter of Space Marines specifically tasked with fighting the daemonic creatures of the Warp and any who have fallen to the Chaos Gods. They act as the miliatary arm of the Ordo Malleus or Daemon hunters. Their existence is unkown to almost everyone. They are organized into several chapters and ranks:
Supreme Grand Master- Highest rank possible for a Grey Knight and has complete power over the brotherhood
Grand Master- Secdon highest rank. There are eight grand masters who control each brotherhood
Grey Knights Captain- Senior officer, and are the chapters foremost warriors.
Terminator- An elite warrior, who fight endlessly against the Daemons of Chaos
Justicar- Lead the latest recruits to the Grey Knights.
Battle-Brother- Equipped with the suit of Aegis Armour and are vying to develop there skills and rank up.