The Secret Police of the Imperium, the Inquisition was created by the Emperor of Mankind in the twilight hours prior to His internment within the Golden Throne. As Terra lay besieged by the traitor forces of Warmaster Horus, the Emperor commanded Malcador the Sigillite to seek out “men of character, skill, and determination” to be tested and trained so that an elite group of investigators might be tasked to discover the alien, mutant, and heretic.

As a completely autonomous Imperial organisation beyond the power of the Adeptus Terra, the Inquisition is immensely powerful. As the Inquisition’s duties involve the scrutiny and policing of the other organisations of the Imperium, the Inquisition itself is answerable to no higher power except the Emperor. No one, except the Emperor himself, is beyond the scrutiny of the Inquisition. This power is officially known as the Inquisitorial Remit or Inquisitorial Mandate.

Inquisitors have the right to call on the services of any citizen or servant of the Emperor. Often an experienced Inquisitor, or one in need of specific services (depending on the current situation at hand), will have a retinue of henchmen that he has deemed most useful. These retinues are made up of individuals drawn from citizens with unique and useful talents, and from the ranks of all Imperial institutions, such as the Ecclesiarchy and Adeptus Mechanicus.

Lady Serillianof the Ordo Xenos stands ready, accompanied by two Inquisitorial Stormtrooeprs.

Within the modern Inquisition there are three Ordos Majoris (Xenos, Malleus, and Hereticus), and an unknown number of Ordos Minoris. Each branch specializes 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 in an Ordo is not mandatory, and there are those Inquisitors who prefer not to join one.

• The Ordo Malleus (The Threat Beyond) – Destroys daemonic threats and investigates the nature of the Daemon. 
• The Ordo Xenos (The Threat Without) – Investigates and eliminates alien influence and plots against the Imperium. 
• The Ordo Hereticus (The Threat Within) – Investigates and roots out heresy, mutation, and rogue psykers from humanity, and polices the Ecclesiarchy.

In addition to the three major Ordos, there are a large but unknown number of Ordos Minoris.

• Ordo Aegis – Remains vigilant over the Cadian Gate.
• Ordo Astartes – Oversees the Adeptus Astartes.
• Ordo Astra – Studies astronomy and stellar information.
• Ordo Barbarus – Monitors pre-Industrial worlds.
• Ordo Chronos – A ill-fated organization, all the members of which vanished.
• Ordo Custodum – Based on Terra.
• Ordo Desolatus – Unknown purpose.
• Ordo Excorium – Monitors Exterminatus.
• Ordo Machinum – Oversees the Adeptus Mechanicus.
• Ordo Maledictum – Oversees issues relating to the Great Rift.
• Ordo Militarum – Oversees the Imperial Guard.
• Ordo Necros – Unknown purpose.
• Ordo Obsoletus – Known to have investigated the destruction of the Cholercaust on Certus Minor.
• Ordo Originatus – Tries to uncover the mystery of the Inquisition’s origins.
• Ordo Redactus – Tries to keep the history of the Inquisition classified.
• Ordo Sanctorum – Oversees the Ecclesiarchy
• Ordo Scriptorum – Monitors Imperial records and communiques.
• Ordo Scriptus – Oversees Imperial historical records.
• Ordo Senatorum – Unknown purpose.
• Ordo Sepulturum – Researches current plagues afflicting the Imperium and determines how best to contain, destroy, and cure them. Created to investigate an increase in outbreaks of the Zombie Plague just before the 13th Black Crusade.
• Ordo Sicarius – Founded to police the activities of the Officio Assassinorum following the events of the Wars of Vindication which resulted from the events of Goge Vandire‘s Reign of Blood.
• Ordo Thanatos – Unknown purpose.
• Ordo Vigilus – Oversees the Ordo Necros.

Inquisitor Gideon Locke of the Ordo Hereticus seeks answers to the riddle of the mutant rebels on Morkai.

Membership in an Ordo Minoris is not mandatory, and there are those Inquisitors who prefer not to join one.

There are several ranks in the orders of the inquisition. However, Inquisitor – The Inquisitor Ordinary, is the vast majority of the Inquisitors are of this rank. Though of relative “lowly” rank, the Inquisitor Ordinary may still call upon any of the Imperium’s vast resources. Inquisitors will recruit their own retinues, and their trainees rise through the three ranks (should they survive long enough).

• High Interrogator – A senior rank of Interrogator, but still short of full Inquisitorial status.
• Interrogator – The second stage for an Inquisitor in training. Interrogators are both capable and strong, having a tremendous will to survive battle alongside their mentors.
• Explicator – The first step of an Inquisitor in training, they learn how to extract information using torture under the direction of their mentor Inquisitor.

Within the Inquisitor’s retinue, the trainees may hold a specific position and fulfill a specific function.

• Legate Investigator – Some Ordos, such as the Ordos Calixis, make use of Acolytes gifted with a formal carta of inquiry and a Sigil of Question, giving them the formal authority of the Inquisition for the duration of a particular investigation.
• Prime – The lead Acolyte of a Warband.
• Throne Agent – The most trusted members of an Inquisitor’s retinue, Throne Agents have ascended to join the ranks of the Inquisition itself, and have both power and responsibility accordingly.
• Trusted Acolyte – Often given positions of responsibility, such as running an Inquisitor’s facilities while they are away or operating in long-term undercover operations.
• Proven Acolyte – After a cell has completed several successful missions, they are inducted more fully into the workings of the Inquisition and can operate more interdependently.
• Acolyte – Servants and aids of Inquisitors. Though not of the rank of Inquisitors, they are nonetheless considered agents of the Inquisition.

— The Gaffer

The Corvus Cluster is a Warhammer 40K  blog documenting our gaming adventures in the fantastical sci-fi universe of Games Workshop.