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"Heresy: such a simple word for such a complex idea. And like so many of the titles bestowed by the followers of the Corpse God, utterly meaningless."

Daemonhost Karnak Zu
Sanguinary Cultist

A mob of Heretics, in this case Sanguinary Cultists of Khorne, on a rampage.

Heresy is defined in the Warhammer 40,000 universe as an opinion, act or promulgation of an ideological doctrine that contradicts the beliefs, theology and the commandments of the Imperial Cult of the God-Emperor of Mankind and the laws of the Imperium of Man.

Since the Imperial Cult serves as the state religion of the Human realm, the Emperor is not just the secular ruler of the Imperium but also the one, true god of Mankind. To take up arms against Him or His faithful agents is more than simple treason, it is a religious heresy.

Thus all enemies of the Imperium can also be deemed "Heretics." Of course this is not always the case, as the Adeptus Ministorum seldom marks people as Heretics for trying to throw off the yoke of Imperial rule or killing an Imperial Guardsman.

Such individuals are simply mundane rebels or criminals and, though their deeds may ultimately hide the taint of the true heresy of the Renegade or Traitor, they are usually dealt with by more conventional forces.

Definition of Heresy

The commission of heresy is often not merely the expression of an unconventional religious viewpoint, but the act of worshiping the Ruinous Powers of Chaos or aiding the forces of Chaos in attempting to subvert the rule of the Imperium.

The worship of any god other than the Emperor is forbidden and those who overtly turn from the Imperial Creed are punished by death, as are those who deny the spiritual authority of the Adeptus Ministorum, the state church of the Imperium. While those men and women who turn to the worship of forbidden gods such as the Ruinous Powers or alien overlords are the most obvious of Heretics, many other variant belief systems have been declared heretical by the Ministorum or the High Lords of Terra throughout the ages.

What does and does not count as heresy is generally determined by the high officers of the Ecclesiarchy. Massive divisions of the Adeptus Ministorum exist to monitor and study the myriad religious sects that exist across the Imperium and determine whether they have remained within the confines of the Imperial Cult's orthodoxy.

The accusation of heresy is often used as a political weapon within the Imperium by those wishing to gain power over others. This can occur at multiple levels. A reasoned debate between brother cardinals can be brought to an immediate end should one of the two hint at accusing the other of heresy. An Imperial diocese that has proven tardy in the raising of tithes can be brought into line by the merest hint of the word.

An accusation of heresy is a blunt tool, and one that can turn upon its wielder, for those accused might have previously unknown allies or political patrons, and outright war between rival factions sometimes results.

There are several variant faiths within the Imperium which the Ecclesiarchy has no choice but to tolerate, even though it disagrees fundamentally with their tenets. The Chapter cults of the Adeptus Astartes are often such faiths, as is the machine-worship of the Adeptus Mechanicus.

Every Space Marine Chapter is faithful to the Emperor and its own ancestral primarch, but they do not usually revere the Emperor as a god. Rather, to them He is but a man, albeit the greatest who has ever or will ever live. This breaks with the single most important tenet of the Imperial Creed, that the Emperor is divine, and has on many occasions proved a source of great tension and even overt hostility between the two Imperial adepta.

On the whole, however, the Adeptus Ministorum and the Adeptus Astartes try to maintain cordial relations, for the Space Marines are the literal genetic descendants of the Emperor through the blood of the primarchs, which flows in their own veins ten thousand standard years after the entombment of the Master of Mankind in the Golden Throne.

The Cult Mechanicus is another deviant faith with which the Ecclesiarchy is often at odds. The tech-priests of the Adeptus Mechanicus worship their own deity, who they call the Machine God. As with the Imperial Creed, many sects exist within the Cult Mechanicus, and it is commonly held that the Machine God is in fact a manifestation of the Emperor in His form as the Omnissiah, the physical avatar of the Machine God in the material universe, although many in the Ecclesiarchy have great difficulty accepting this.

Other Mechanicus sects appear to outsiders to be saturated in idolatry, worshipping the very machines they are tasked with maintaining and committing a thousand other spiritual transgressions punishable by death by the laws of the Adeptus Ministorum and the Imperium. Despite such differences, the Ecclesiarchy has no choice but to tolerate the Cult Mechanicus, just as the Emperor during the Great Crusade had to ironically accept their deviance from the atheistic Imperial Truth, for without the tech-priests the Imperium would literally grind to a halt.

No Imperial institution can do without the Adeptus Mechanicus, just as none forgo the services of the Adeptus Astra Telepathica or the Navigator Houses, regardless of how distasteful the faithful might find their psychic servants.

The Ecclesiarchy is especially interested in those that not only reject the Emperor, but also embrace something else in His place. These slaves and servants to xenos and Warp entities are viewed as true Heretics and their discovery and eradication is a prime goal of the Ministorum throughout the Imperium. Finding such Heretics can, however, be a difficult task. Amidst the thousands of Imperial cults and saints, it is easy for seemingly faithful practises to mask heretical deeds.

To a certain degree, the Ministorum polices its own ranks against this corruption, but it is an impossible task keeping tabs on a church that spans tens of thousands of light years and countless worlds. Even those who obviously seem to bear taint are not always guilty.

Psykers and mutants, for instance, are two groups that often bear the suspicion of heresy, sometimes unfairly, sometimes not. While it would be convenient to brand all of these individuals as an affront to the Emperor and a scourge upon the Imperium, they are far too integrated into Imperial society to purge them wholesale.

As a result, the Ministorum and other Imperial forces such as the Inquisition must rely on investigation and intelligence-gathering. Planets and their populations must be watched and monitored for signs of taint. Saints and cults must be screened and rumours of dark deeds investigated. No person is beyond the suspicion of the Inquisition, not even the great Space Marines of the Adeptus Astartes.

Acts of heresy are categorised in legalistic grades (1st, 2nd, 3rd, etc.) which differ based on the severity of the act. Punishments range from imprisonment, assignment to an Astra Militarum Penal Legion, excommunication from the spiritual rites and protection of the Ecclesiarchy, execution, and arco-flagellation, to name but a few.

Dealing With Heresy

Inquisition Acolytes often find themselves presented with the question of whether or not someone or something is heretical. However, by the time the agents of the Inquisition have become involved, there is a good chance that something foul is afoot.

In any case, they must still try and identify the true Heretics from the simple malcontents. It is taught by the Inquisition that there are three stages to the identification and eradication of heresy. These are suspicion, investigation and purging.


"From a single seed of doubt can grow a world of heresy."

— Taken from Adeptus Ministorum teachings

Often the only clue an Acolyte has to the presence of heresy is through his or her instincts. The Ecclesiarchy and the Inquisition both encourage investigators to follow these feelings, believing it is the divine will of the Emperor guiding them to His enemies.

This, combined with the broad powers of a secret police organisation like the Inquisition, means that few people are safe from scrutiny when it comes to the rooting out of heretical behaviour.

Acolytes are taught that no one and nothing should be above their suspicion, which can lead to them becoming extremely paranoid, another "virtue" encouraged by the Inquisition.


Once a target has been identified, the next step is to begin an investigation. In many cases, especially within the ranks of the Inquisition, the gathering of evidence is secondary to identifying guilty parties. Such clues are more to help lead the investigator to their quarry rather than prove anything in particular once they get there.

Because it is vital the Heretics be discovered and uprooted, the most important aspect of many investigations becomes stealth. Quite often, even the hint of Acolytes nosing around sends cultists underground, vanishing into the general populace and becoming practically impossible to find.

As a result, the Inquisition especially advocates striking against Heretics as soon as possible, even when there is only the most circumstantial of evidence. In the end, any number of innocent deaths is acceptable if it means a true Heretic is found and destroyed, preventing the death, corruption or damnation of tens of millions more.


"Intolerance is the only appropriate reaction to heresy."

—Taken from Adeptus Ministorum teachings

Once the heresy has been unmasked the next step is to eradicate it. This can be harder than it seems, as, like weeds, many heretical cults can appear to be destroyed only to spring up once more. The teaching of the Ecclesiarchy and the Inquisition on this matter is clear: the Emperor rewards thoroughness.

If there is the slightest suspicion of involvement in the heresy, they must be purged. Sometimes the heresy has consumed an entire hive city or continent, and the Ecclesiarchy cannot be so discerning as to single out individuals.

At this point, the Imperium shows no mercy and offers no quarter, leading to the destruction of entire cities or even worlds through military conflict, atomic fire or Virus Bomb. Better a dead world than one that does not bow to the Emperor -- or worse, serves His enemies and the enemies of all Mankind.

Punishments for Heresy

Excommunicate Traitoris

"The worst enemies are those we make ourselves."

— Imperial Thought For the Day

The term Excommunicate Traitoris is a High Gothic bureaucratic designation that represents the highest form of Imperial reproach against an Imperial citizen, world or organisation that has committed extreme acts of heresy against the Imperium, including mutation, rebellion against Imperial rule and corruption by Chaos.

It is the ultimate form of censure: a Traitor so designated is officially banished from the Imperium on pain of death and cast from the light of the benevolence of the Emperor. There is no graver fate for those that serve the Imperium.

When an individual or organisation is declared Excommunicate Traitoris by either the High Lords of Terra or an Inquisitor of the Holy Ordos of the Inquisition, the accused is struck from the annals of Imperial history.

Their names are deleted from the scrolls of honour in the Hall of Heroes in the Imperial Palace and wiped from the memories of the Librarium Terra's databases and other Imperial archives by the Deletion Teams of the Administratum's Historical Revision Unit.

If the accused is an individual Astartes or an entire Chapter of Space Marines, the gene-seed stores from that Chapter held by the Adeptus Mechanicus will be destroyed and if any of the Heretic Astartes are slain, their bodies will be incinerated so that their blood will no longer taint Mankind.

However, if an accused Heretic confesses their sins against the Emperor and repents their misdeeds, their deaths are quick and clean. But more often than not, the accused Traitors flee for their lives, usually towards the hell-storms of the great Warp rifts such as the one in the Segmentum Obscurus known as the Eye of Terror or the Malestrom in the Segmentum Ultima.

With no sanctuary to be found within the realms of Humanity, they will be forever hunted for the rest of their days or executed on sight by any and all loyal servants of the Imperium.

Edict of Obliteration

An Edict of Obliteration, also known as a Damnatio Memoriae in High Gothic, is a frequent component of major political or religious changes within the Imperium. The term encompasses the more specific destruction of images of a member of the Imperial elite after their death or overthrow.

The result of an Edict of Obliteration is to have the offending individual effectively erased from Imperial history. The purpose of an Edict of Obliteration is to preserve the honour of the Emperor by removing every trace of the aforementioned Persona non Grata who damaged Humanity from the life of the Imperium, as if he or she had never existed.

In a galaxy-spanning empire that stresses fealty and loyalty to the Emperor in return for advancement, acclaim and spiritual salvation for its elites, this is perhaps one of the most severe punishments. This is especially true for those Imperial adepta that directly serve the Emperor, such as the Ecclesiarchy, the Inquisition, and the members of the Imperial military forces like the Adeptus Astartes, the Navis Imperialis and the Astra Militarum.


"Some may question your right to destroy ten billion people. Those who understand realise that you have no right to let them live."

Exterminatus Extremis

The order of Exterminatus is a death knell for a world, a last resort for the direst of situations. It calls for the complete eradication of all life on an Imperial planet. Such a command can only come from the highest ranks of the Imperium -- a Space Marine Chapter Master, Lord High Admiral of the Imperial Navy, Lord Commander of the Astra Militarum or an Inquisitor.

It is a grim measure, and the orders unleashing such catastrophic destruction are only issued when the threat is determined to be a possible or actual extinction-level event so prevalent on the affected planet that no other acceptable solution or redemption can be envisioned or attempted.

It has been used to combat planet-wide heresy, rampant, uncontrollable mutation or disease, to prevent the opening or widening of Warp rifts, or when xenos are so entrenched that the resources of the affected world (population included) are beyond salvation.

Examples of Heresy

  • Worshiping other gods besides the Emperor, who is the one, true god of Mankind, especially the Chaos Gods. This does not include the Machine God who is worshiped by the Adeptus Mechanicus as a facet of the Emperor in the form of the Omnissiah and whose religious and political autonomy is protected by the ancient Treaty of Mars signed in the late 30th Millennium. Nor does this include the Adeptus Astartes, as the various Chapters have different views on the Emperor's so-called "divinity," and usually venerate the Emperor not as a divine being, but rather as the pinnacle of Humanity to have ever come into existence.
  • Treason or rebellion against the rightful rule of the Imperium and its Emperor.
  • The usurpation of power within the Imperial adepta from the rightful agents of the Emperor. See the Horus Heresy and the Reign of Blood for the most infamous examples of this type of heresy.
  • The use of alien technology or any other technology not approved by the Adeptus Mechanicus. However, the Mechanicus is legally entitled to confiscate all alien technology or rediscovered archeotech for research and development purposes.

Heretical Cults

Heresy can be a contagious thing in itself, and when it spreads, a cult is often formed from those that subscribe to it. In other cases, a powerful or charismatic leader will often draw a coterie of devoted disciples and followers into forming a heretical cult, and by the same token, deviants and like-minded individuals often join together for mutual support and protection.

Cults exist in the main for very good reasons, the most obvious being secrecy -- the protection and greater resources of the larger group allows it to better organise and conceal itself from prying eyes, rivals, and outside threats. The second is power, as the strength of a cult's membership united is often far greater than what an individual would possess.

This is a truth that remains constant on many levels, from pooled finances to sustaining and reinforcing the loyalty and adherence of its members. Isolation, after all, promotes cohesion in-and-of-itself, whilst division will destroy a cult as easily as any Witch Hunter's purge.

Heretical cults often share several common attributes despite their many doctrinal differences. Most seek to conceal themselves behind the disguise of a more benign (or at least accepted) front organisation, or remain completely hidden from the authorities in order to avoid discovery. Cults also often favour a particular milieu in which to operate and recruit fresh members, which is often determined by the cult's own nature.

For example, a cult centred on fermenting rebellion amongst mutant labourers will confine itself to the shatters and barrens where the mutants dwell, recruiting from the disaffected and outcasts among their numbers. Meanwhile a malefic conspiracy of Daemon-worship among the depraved nobility will often limit itself to the salons and private estates of the elite for its haunts and recruiting grounds.

Many cults also share similar organisational structures despite their differing goals and natures. Each has its own strengths and weaknesses, and in many cases, the structure may involve many minor differences in practice and effect. While a particular cult may favour one structure over another, it will often include other structural elements as well.

Charismatic Cults

Charismatic cults are the simplest in structure, as their organisation is based around the authority of a single figure -- the cult's leader. Personal authority is usually the norm in these cults and is maintained by the leader's force of character, natural charisma, oratory skills, or simple personal power.

Cults led by a single powerful figure such as a witch or sorcerer are often of this type, although any place where malcontent or religious schism breeds can throw up a charismatic leader. This individual will exploit the weaknesses of others for their own personal power or gratification, or the fulfilment of their own apocalyptic vision.

Mystery Cults and Secret Societies

Mystery cults are centred, as their name implies, on secrets. These secrets may concern a hidden network of power, a cache of forbidden lore, access to ancient prophecies, or other esoteric truths and important information. These secrets are held by a select group, forming an inner circle or oligarchy (often with several sub-tiers of rank), and are the foundation of their power and authority.

The cult's members must submit to this group's leadership and direction if they are also to gain access to the hidden secrets, and perhaps one day wield the cult's power for themselves. Many mystical cults, religious sects, and those focused on occult lore follow this pattern, as do a surprising number of institutions who hide their inner workings with elaborate ritual and labyrinthine secrecy.

Within the Imperium, arguably the largest single mystery cult is actually the Cult Mechanicus. The Priesthood of Mars hides its secrets well, even from its own numbers.

Cellular Cults

Perhaps the most efficient structure for a cult carrying out activities that risk regular exposure and persecution is the "cellular structure." This kind of cult's structure breaks down its membership into a series of small sub-groups, the cult's cells.

Cells, which range from a handful of individuals up to perhaps hundreds of members, are each devoted to carrying out a particular specialisation or a certain task or goal. Other than the select few, or an individual, who control the cell, none of the cell's other members has any direct contact with the wider cult or even other cultists outside of his immediate circle and cell.

This structure has the profound advantage that if any of its rank-and-file are captured or compromised, they may betray nothing that does not concern their own immediate cell, keeping the wider cult safe and its dealings and purposes secret.

Indeed, this shell game may be carried further, with a particular cell's leadership forming the rank-and-file of another, smaller cell senior in authority, and that cell's leadership part of another and so on.

This can prove a phenomenally hard structure to successfully track and destroy and by its nature is highly adept at covert and independent operations. Many of the most dangerous cults and heretical groups who are sufficiently well-organised operate a cell structure or at least organise their field agents into cells for this reason, as does, ironically enough, the Inquisition itself.

See Also


  • Dark Heresy: Blood of Martyrs (RPG), pp. 21-22
  • Dark Heresy: Disciples of the Dark Gods (RPG), pp. 22-25
  • Dark Heresy: The Inquisitor's Handbook (RPG), pp. 204-205