NHCC Dark Heresy
The Holy Orders of the Emperor's Inquisition, more commonly known as the Inquisition, are a secretive and powerful organization of the Imperium responsible identifying and destroying the myriad of potential threats to the Imperium and humanity. Inquisitors hunt down heretics, traitors, alien infiltrators and even daemons. They necessarily exist beyond the Adeptus Terra, as part of the Inquisition's role involves rooting out corruption and gross incompetence from the Imperium itself. They answer only to the Emperor and to themselves.
Within the modern Inquisition of M41 there are three Ordos Majoris;Xenos, Malleus, and Hereticus, and an unknown number of Ordos Minoris. Each branch specialises in the combat and investigation of specific threats to the Imperial domain. While Inquisitors from any Ordo are trained to deal with all potential dangers, it is the role of the Ordos to produce agents who are particularly adept at understanding and destroying specific abominations. Membership of an Ordo is not mandatory, and there are those Inquisitors who prefer not to join one.
Ordo Malleus (The Threat Beyond): Destroys daemonic threats and investigates the nature of the Daemon. The Ordo came into being immediately after the Horus Heresy, and therefore has been a part of the Inquisition from the beginning.
Ordo Hereticus (The Threat Within): Investigates and roots out heresy, mutation and rogue psykers from humanity, and polices the Ecclesiarchy. The Ordo Hereticus was founded following the events of the Age of Apostasy.
Ordo Xenos (The Threat Without): Investigates and eliminates alien influence and plots against the Imperium. It is not known when the Ordo Xenos was founded, however it is believed to be of a similar age to the Ordo Malleus.