The The Holy Orders of the Emperor's Inquisition is a secretive and powerful Imperial organization commited to the protection of the souls of humanity. Its best agents are known as Inquisitors.
There are three major Inquisitorial schools, the Ordos Majoris, each specialised in a particular enemy.
- Ordo Xenos: dedicated to the investigation and elimination of aliens and alien influences within the Imperium.
- Ordo Malleus: dedicated to the investigation and elimination of Daemons and daemonic influences within the Imperium.
- Ordo Hereticus: dedicated to the investigation and elimination of heretics, mutants and rogue psykers.
Each of the Orders has a military arm, the Chamber Militant.
- Deathwatch: a force composed of veteran Space Marines from various chapters. They serve Ordo Xenos.
- Grey Knights: an elite all-psyker Marine Chapter. They serve Ordo Malleus.
- Sisters of Battle: an all-female armed force. They serve Ordo Hereticus.