The Ephesian Schism
The Inquisition (The Holy Orders of the Emperor’s Inquisition) is a secret organisation that exists outside the standard administrative hierarchy of the Imperium of Man.
The Inquisition acts as the secret police force of the Imperium, hunting down any and all of the myriad threats to the stability of the God-Emperor’s realm, from the corruption caused by the Forces of Chaos, heretics, mutants and rebels, to assaults from vicious alien species like the Tyranids, Orks or Dark Eldar. The Inquisition’s infamous sigil was derived from the personal heraldry of Malcador the Sigillite, the Regent of Terra during the Great Crusade and the Horus Heresy and the second most powerful psyker in the Imperium of Man after the Emperor of Mankind himself. It was Malcador who first created the secret organisation that would later become the varied Ordos of the Inquisition at the start of the Heresy on the orders of the Emperor.
The Master of Mankind had ordered the Sigillite to find a group of men and women of an “inquisitive nature” to search out the enemies of the Imperium, whether they lay within or without.
The Inquisition is immensely powerful, and the only individual that is exempt from its scrutiny is the Emperor himself. If he has good cause, an Inquisitor may demand any service from any Imperial citizen, up to and including the High Lords of Terra. The Adeptus Custodes who guard the Emperor’s palace and person are exempt from conscription, because their duty to the Emperor is clear and unchanging. When it comes to the Adeptus Astartes, Inquisitors often show some discretion, as Space Marines are often willing to come to blood over any infringement on their Emperor-granted autonomy.
However, not even the Adeptus Astartes are immune from the Inquisition’s scrutiny and justice, and entire worlds have been destroyed in order to cleanse them if they were deemed traitorous.
Inquisitors also have absolute power to judge and execute supposed heretics, mutants, unsanctioned or rogue psykers and the like, with no appeal save the intervention of another Inquisitor. Practically, all possible verdicts are death sentences, although the means by which they are achieved differ.
Traitors, the worst grade of offenders, are considered irredeemable and will be quickly executed.
Heretics may be redeemed, often after considerable amounts of torture, and may receive absolution through death in service to the Imperium. This service may consist of arco-flagellation, conscription into Imperial armies, becoming the operator of one of the Adeptus Ministorum’s Penitent Engines or, in the case of penitent psykers, being sent to Holy Terra to become new psychic fuel for the Golden Throne.
Certain traitors deemed useful to the Inquisition may in extremely rare cases be mind-scrubbed, their old memories and identity erased and replaced with one loyal to the Inquisition. If it is beyond their means to track down and kill a particular individual or organization, an Inquisitor can simply declare the offending entity Excommunicate Traitoris, stripping them of whatever rights they may have had and as such marking them as a target fit for extermination by any and all loyal servants of the Emperor.
If the Inquisitor deems it necessary he or she can attach an official stigma to a dangerous heretic, Traitor or alien race. Each of the major Ordos has a different official stigma which pertains to their primary enemies. These stigmata include the Extremis Diabolis for the Ordo Malleus, the Xenos Horrificus for the Ordo Xenos and the Hereticus Abomini for the Ordo Hereticus.
The Inquisition will also use its delegated power from the High Lords of Terra to declare “tainted” Space Marine Chapters or other Renegade Imperial military units or individuals Excommunicate Traitoris. The Chapter or other unit will then usually be hunted down by the Grey Knights or the Sisters of Battle, usually resulting in the Chapter fleeing to the Eye of Terror or the Maelstrom (if it has not already done so).
Young psykers who have not worked against the Imperium or used their powers much will usually be repeatedly tested, and if they are young, strong and pious enough, may be taken in by the Black Ships of the Inquisition to become a Sanctioned Psyker or even an Inquisitor. The requirements are strict and many will be found wanting. Those that fail the Inquisition’s tests will either be executed or used to power the vast psychic beacon of the Astronomican, their lives sacrificed for the ultimate good of Mankind to sustain the Golden Throne which keeps the Emperor alive.
If a world is the subject of extreme corruption by Chaos, an Inquisitor may call down the verdict of Exterminatus, destroying all ecosystems on the planet and rendering the world completely lifeless. Many question the necessity of such acts, but the Inquisition feels fully justified in performing them. They feel that it is better for countless servants of the Emperor to be sacrificed than to let a single heretic escape their wrath to endanger more lives.
Typically, though, such an act is reserved for only the most extreme cases, such as a massive outbreak of Chaos activity that threatens to corrupt other worlds or unchecked infiltration by Genestealer Cults that precede (or can cause) a Tyranid invasion that will consume an entire sector.