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"The warp is a strange and terrible place. You might as well throw a traveller into a sea of sharks and tell him to swim home as send him through the warp unprotected. Better it is not to let common man travel through the stars. Better still, let him not know such a thing is feasible."
— Fra Safrane, 5th aide to Navigator De'el.
Notable warpstorms

Notable Warp Storms in the galaxy between the 35th and 41st Millennia

The Immaterium (also referred to as the Empyrean, the Aether, the Sea of Souls, the Realm of Chaos, Warpspace or most commonly, the Warp) is an alternate dimension of purely psychic energy that echoes and underlies the familiar four dimensions of the material universe. It is the source of all psychic powers and known instances of so-called "sorcery" or "magic" as well as the home dimension of the Chaos Gods and their myriad daemonic servants. In fact, the terms "Chaos" and "the Warp" are often used interchangeably by those aware of their existence within the Imperium of Man. Superficially, the Immaterium is Mankind's solution to the problem of faster-than-light travel, an equivalent to the Star Wars universe's dimension of hyperspace. This function as a faster-than-light medium for space travel is achieved because the Immaterium is a domain of pure psychic energy, with spacecraft navigating between its currents, as in an ocean. The psychic energy that makes up the Immaterium is believed to be the direct result of the existence of sentience in the universe, in particular the intelligent species of the Milky Way Galaxy. Considered to be a dark reflection of the material universe, the Warp is an ocean of chaotic psychic energy, raw emotion given physical form. Stirred by emotion and action, the Immaterium is the true Realm of Chaos, home to the Dark Gods who comprise the Ruinous Powers and their legions of daemonic followers. The Immaterium is also rumoured by many cultures, human and xenos alike, to be the final resting place of the spirits of the dead, and therefore can be considered the "Underworld" of the Warhammer 40,000 universe.

Warp Travel


Space Marine Legion warships emerge safely from the Warp into realspace during the Horus Heresy

A spacecraft drops into the warp by activating its warp engines. As a ship leaves the material universe it enters a corresponding point in warpspace. The ship is then carried along by the tides and currents of the warp. After travelling in this fashion for an appropriate time, the ship uses its warp engines to drop back into realspace. Because the material universe and the warp move relative to one another, the ship reappears in a new position several light years from the starting point. This process is called a jump or a hop, and the process of entering or leaving is known as a drop, shift, or translation.

Journeys are undertaken in short jumps of up to four or five light years. Longer jumps are unpredictable and dangerous. The tides of warpspace move in complex and inconsistent patterns, and ships attempting longer hops often end up widely off course. Were this limitation to apply to all warp travel, then Humanity would not have spread throughout the galaxy as it has. It is possible to make long jumps of many light years by steering a ship in the warp itself—sensing, responding to, and exploiting its currents and thereby directing the craft towards a corresponding point in the material universe. Only the strain of human mutants known as Navigators can pilot a craft through the warp in this way.

Some individuals are sensitive to the movements of warpspace. They can, for example, sometimes tell that a spacecraft is approaching even before it drops back into the material universe. Human sensitivity to the warp is not generally well developed. However, in a minority of people this sensitivity is far more finely tuned. These people are known as psykers, and they are able to consciously control and use the energy of the warp to affect the material universe. Navigators possess gifts of a specialised kind who can use their powers to steer spacecraft in the warp.

The Astronomican and the Warp

The Astronomican is a psychic homing signal centred upon Terra. It is powered by the continuous mental concentration of a thousand psykers. The Astronomican cannot be detected in the real universe—only in the warp. It is by means of this signal that the Navigators can steer their spaceships over long distances. The Astronomican’s signal is strongest close to Terra and gets increasingly weaker further away. It extends over a spherical area with a diameter of about 50,000 light years. The Astronomican does not extend to the extreme fringes of the galaxy, and because Terra is situated in the galactic west, its signal does not reach a massive swathe of the eastern part of the galaxy at all. Nor is the extent or strength of the signal constant—it can at times be blocked by localised activity within the warp itself. Such activity may be compared to the hurricanes or storms of a terrestrial weather system and is known as a warpstorm. Warpstorms may be so bad, and so long-lasting, that entire star systems are isolated for hundreds of years at a time.

A warpstorm not only obscures the signal of the Astronomican, it is also dangerous for spacecraft travelling nearby. No spacecraft can venture within a warpstorm and expect to survive, although there are tales of miraculous escapes and of ships being thrown tens of thousands of light years off course. Warpstorms are not the only dangers within the warp. There are sentient energies and other immaterial life-forms that inhabit it, creatures formed from, and part of, the shifting stuff of the warp. Few are friendly and many are hostile. They are known to Mankind as daemons.

Time Displacement

The time differences between real space and warp space are quite drastic. Not only does time pass at different rates in both kinds of space, but it also passes at very variable rates. Until a ship finishes its jump, it is impossible for a ship’s crew to know exactly how long their journey has taken. Time passing in real space is referred to as real time. Time passing on board a spacecraft is referred to as warp time.

Warp Navigation

Once a spacecraft activates its warp drives, it is plunged into a dimension very different from the material universe. It is convenient to imagine warp space as consisting of a relatively dense, almost liquid, energy, devoid of stars, light and life as it is commonly known. Once within warp space a ship may move by means of its main drives, following powerful eddies and currents in the warp, eventually reaching a point in the warp corresponding to a destination in real space. The most difficult aspect of warp travel is that it is impossible to detect the spatial movement of warp space once a ship is in the warp. The ship can only blindly carry on, its crew trusting that it is going in the right direction. The longer a ship remains in warp space, the greater the chances of encountering some unexpected current that can turn it unknowingly off-course.

Navigation of warp space can be achieved in two ways: the calculated jump and the piloted jump.

All warp-drives incorporate navigational mechanisms. When the ship is in real space, these monitor the ever-shifting movements of that part of the warp corresponding to the ship’s current position. It is a ‘window’ into warp space. By means of observing these movements in the warp it is possible to calculate a course, corrective manoeuvres, and approximate journey time to a proposed destination. Calculation relies on the assumption that the warp-currents observed from real space don’t change significantly during flight. This method is known as a ‘calculated jump’. It is not safe to make a calculated jump of more than four light years at one go. The longer the jump, the greater the chances of a significant change in warp current movement.

The second, and more efficient, form of warp-navigation is the piloted jump. This method relies upon two factors: the Navigators and the psychic beacon of the Astronomican. The Astronomican is centred on Earth and is not only controlled by, but is directed by, the psychic power of the Emperor. The Astronomican is a psychic beacon that penetrates into warp space. A Navigator on board a ship in the warp is able to pick up these signals and can steer a spacecraft through warp space, compensating for current changes as he does so. A piloted jump can cover a far longer distance than a calculated jump. Most piloted jumps are no more than 5,000 light years at a time, but longer jumps have been made.

A typical interstellar voyage might begin with a cargo ship lying in orbit around an Imperial world. Tiny shuttlecraft busily transfer precious minerals, foodstuffs, crew, and manufactured items from the world below. The loading procedure may take days or weeks, as the shuttles return time and time again to the huge ship. Once loading is complete, the colossal craft slowly accelerates out of orbit under the power of its main drives. The ship heads outwards towards the rim of the solar system, carefully increasing speed by tiny increments as it does so. Although the vessel’s engines are capable of terrific acceleration, the risk of collision with inter-planetary debris is high if the ship accelerates too quickly or too much. As the sun shrinks in the ship’s wake, the density of debris lessens and the ship’s speed reaches approximately one percent of light speed.

After several weeks of travel, the ship arrives at its first destination. This is the ‘jump-point’ lying around the star system like the circumference of a circle. This delineates the point at which inter-planetary debris falls below maximum warp density. Once this invisible line has been crossed, it is safe to activate warp engines. A crew careless or foolhardy enough to prematurely activate warp-drives would be lucky to find their ship hurled thousands of light years off course. More likely, the ship would be torn apart and destroyed, never to be heard of again.

With the safe activation of its warp-drives, the ship is plucked out of the real universe and enters the dimension of warp space. Its true interstellar journey has begun. Ships travelling in warpspace do so by means of jumps varying in length up to 5,000 light years. Only a long journey would involve more than a single jump. Even so, almost two weeks pass onboard ship before the craft is ready to end its jump. Meanwhile, because of time shifts in warp space, over a year has passed in the real universe.

The ship re-enters real space just beyond the jump-point of its destination solar system. If it is lucky, the ship will come out close to the jump-point, otherwise it may take many extra weeks to reach the inner planets. It is always wise to allow a safe margin when jumping towards a star. The results of reentering space within the jump-point would be the same as prematurely activating warp drives on the outward journey, and would almost certainly end in disaster. The ship is now ready for its final haul, beginning by broadcasting to its destination and establishing a new time coordinate. Time in warp space is so different from time in normal space that the crew has no idea whether their journey has taken a few months or years. Initially, the ship travels at approximately one percent of light speed, decelerating gradually through the denser inner regions. Eventually, the ship reaches its destination, where swarms of tiny shuttles once more make themselves busy loading and unloading cargo and passengers in preparation for the ship’s next journey.

Warpspace Channels

In theory it is possible to travel anywhere through warp space. However, the shifting tides of the warp make it easier to travel from some systems to others, and short warp jumps are always more accurate than longer ones. This is particularly true when moving a large fleet, which may become spread out across several light years of space over an extended journey. Long established and well-charted warp space channels connect star systems and entire regions, providing relatively predictable conduits through which the majority of shipping passes.

Warp Gates

Warp Gate

A Tech-Priest discovers a Warp Gate

A warp gate is a point in real space which is linked to another point in real space by a tunnel through warp space. The tunnel somehow avoids the normal disturbances of warpspace, allowing a journey to be made within a fixed time and in perfect safety. The existence of warp gates represents something of a mystery, and much debate rages over whether they are natural or artificial. If artificial, then none can say who made them or for what purpose. Furthermore, some warp gates have been artificially enhanced, their entrances delineated by mechanical constructions whose exact function can only be guessed at. Other warp gates are mere black holes in space.

Warp gates occur in the depths of space, at the boundaries of solar systems, within solar systems, and even on planets. The largest are easily big enough to permit the passage of spacecraft and are usually situated at the edge of a solar system or amongst its outer planets. Other gates are only large enough to permit the passage of small vehicles, or perhaps human-sized creatures. These occur mostly on planet surfaces and lead directly to other gates on the surfaces of other planets. All gates are rare, the smaller types extremely so. Planetary gates are often disguised, or respond only to electrical, psychic, or other signals, which would seem to indicate a certain amount of intended secrecy on the part of their builders.

All space-going races are prepared to utilise warp gates when they find them, although discovering where they lead can often be hazardous. Many gates appear to be defective, and can dump a ship randomly into warp space. Others can lead to places which may once have been stars or planets, but which are now no more than empty space. The possibility of emerging into a distant, hostile alien star empire also has to be considered. It may be that craft vanishing into warp space have been transported beyond the galaxy itself. Warp gates often become extremely important to whomever controls them, and many are of vital strategic value to the Imperium. Imperial Commanders and other interests vie for control of a warp gate in their sphere of influence, and these relics are often heavily defended against outside attack.

Warp Portals

A warp portal is a point in space where the warp and real space interface, forming a stable entrance into, and exit from, warpspace. It is not necessary to activate a warp drive to enter the warp in this manner, although any vessel not equipped with warp shields would be unlikely to survive for long within the empyrean. It does not lead to a tunnel, and a spacecraft entering a portal is cast to the chance currents of warp space. With careful manoeuvring it may be possible to re-enter normal space using the same portal from the other side. Again, the exact nature of the portals is not understood, and no one knows whether they are mere accidents or have some secret purpose. Some aliens use warp portals to travel between warp space and real space, specifically the creatures known as Enslavers, which live within warp space itself. Like warp gates, portals occur in all places and may appear on a planet’s surface. Some have a definite physical constituent, whilst others are invisible or take the form of a hole in the ground or a dark cave mouth. Warp portals do have their uses, for there are recorded instances of spacecraft with damaged warp drives, trapped within the warp and doomed to destruction, suddenly locating a warp portal enabling them to return to real space.

Realm of Chaos

Realm of Chaos

A look into the hellish Realm of Chaos

The Ruinous Powers of Chaos and their daemonic servants are known to inhabit the portion of the Immaterium often called the Realm of Chaos. Daemons are only able to exist within the Immaterium, unless certain conditions are met within the material realm. The Immaterium is what empowers the daemonic and mortal servants alike of the four Dark Gods -- Khorne the Blood God, Slaanesh the Prince of Pleasure, Tzeentch the Architect of Fate, and Nurgle the Lord of Decay -- and their followers will undertake any action to increase this power and their standing with their unholy masters. Each of the Chaos Gods maintains his own kingdom within the Realm of Chaos, the nature of which matches his own personality and interests exactly. The Realm of Chaos is marked by nearly constant warfare and strife between the daemonic servants of the Ruinous Powers, who constantly scheme and battle against once another in an eternal struggle for dominance that can never be won. The Chaos Gods and their servants are consumed by this struggle and in truth pay very little attention to the doings of realspace, save when the actions of mortals either present a threat to all of the Chaos Gods' continued activities or an opportunity for the Ruinous Powers to enhance their position against one another in their eternal conflict.

Formless Wastes

The Formless Wastes, also known as the Chaotic Abyss and the Land of Lost Souls, are those regions of the Immaterium that do not fall under the dominion of one of the four Chaos Gods. Much of its landscape is simply a terrain of pure chaos that is forming and reforming constantly based on the psychic currents roiling the minds of the sentient mortals of the Milky Way Galaxy as well as the psychic currents of the Realm of Chaos. The Formless Wastes are a place where the laws of physics hold no sway. Within the Formless Wastes sit rivers of tar that flow through petrified woodlands beneath crimson skies. Great stairways ascend into the heavens where they connect back on themselves in an endless loop. These celestial stairways sit alongside castles crafted from bone and fortresses of ichor while pillars of fire burn on the horizon. Every dream, nightmare and vision ever had by one of the sentient races of the galaxy has a representation within the Formless Wastes. The Wastes are also the home of the daemonic Furies who watch for any prey, mortal or daemon, that comes within their reach.

Those Greater Daemons and Daemon Princes that are strong enough to maintain a level of psychic control over their environment within the Warp also make their homes within the Wastes. These islands of horrific stability stand out within this chaotic wilderness with some only appearing for an instant whilst others are as old as the Ruinous Powers themselves. Each of these sub-realms is a small extension of the Realm of Chaos that embodies the whims of its creator and has a shrine or temple dedicated to its beliefs. Some are even populated by daemons born from the mind of the Greater Daemon or Daemon Prince, though these entities are usually short-lived as they tend to be consumed by the Furies that populate the Formless Wastes and are much weaker than the daemons of the four major Chaos Gods.

The minor Chaos Gods are also believed to sometimes maintain their demesnes within the Formless Wastes. Also within the Formless Wastes of the Immaterium resides the dark daemonic foundry known as the Forge of Souls.

Psychic Realm

The Immaterium is a dimension of the spiritual, created, sustained and influenced by intelligent mortal emotions and actions in the physical universe. The mind of every sentient being in the material universe save the Necrons and the C'tan leaves a psychic imprint within the Immaterium, and although the signature of one mind is almost insignificant in the energy or influence it generates, when the imprints of an entire intelligent race of billions upon billions of individuals are combined they have a huge impact on the very nature and shape of the Warp (this seems to imply that the Immaterium is not chaotic by nature, but has been made so by the chaos and war that defines so much of the material realm). When an emotion or faith in an entity or concept grows strong enough, it actually becomes one of the denizens of the Warp. Many of these beings vanish when the emotion or beliefs that create them pass, but the strongest and most archetypal can become self-perpetuating, spreading the thoughts and events that grant them form and power and even interacting with the material world in a way that further strengthens the beleifs and attitudes that give them existence. The strongest of these beings become the gods and daemons associated with a specific group or culture, and almost every single intelligent race or force of will has its universal concepts or religious figures personified in some way by the Warp, be they Chaos, Eldar, Ork, or human.


The extrasensory, seemingly magical abilities of the psychically-gifted individuals known in the Imperium of Man as psykers are powered by the energies of the Warp, and when such power is used, the daemons and creatures of the Immaterium are drawn to the psyker's mind like moths to a flame. Those humans trained in the use of the psychic arts are able to resist such incursion to a degree, but the greatest fear of the Inquisition is the fact that an untrained human psyker of sufficient power can become the target of daemonic possession -- and a gateway for the intrusion of the daemonic servants of the Ruinous Powers into the physical world.

Realm of the Dead

Many cultures of the Milky Way Galaxy, both human and xenos, believe that the Immaterium is the final resting place for the souls or spirits of the dead. Certainly there is some truth to this notion. The Eldar believe that upon their deaths, their souls travel into the Warp where they are immediately devoured by their race's ancient enemy, the Chaos God Slaanesh. Because the Eldar's hedonistic and intensely psychic nature was responsible for bringing Slaanesh into existence within the Empyrean following the Fall of the Eldar sometime between the 29th and 30th Millennia, it can be said that Eldar souls have a form of "psychic gradient" in which they are immediately consumed by the hunger of Slaanesh upon the death of their physical bodies if protective measures are not taken. For the Eldar of the Craftworlds, this protection takes the form of the Spirit Stone worn by every one of their number which immediately absorbs their soul's psychic energy upon death so that it can later be deposited for safekeeping within their Craftworld's Infinity Circuit. There it will exist for all eternity as part of a gestalt collective mind of the dead. The Dark Eldar take a predictably more savage course. They are partially protected by their existence within the Labyrinthine Dimension of the Webway from consumption by Slaanesh, but "She Who Thirsts" will eventually consume even a Dark Eldar's soul unless he draws psychic energy to protect himself from the psychic agony of others. It is for this reason that the Dark Eldar are such malevolent creatures, seeking out an endless supply of slaves whose torture they not only enjoy but which actually keeps their twisted souls intact.

Amongst the mortal servants of the Chaos Gods, there is no doubt: when a mortal dies in realspace, his soul is immediately swept into the Warp at the moment his physical body dies, where it will be devoured by the daemons and other Warp entities or made into their pitible plaything for all eternity. The only salvation from this grim fate is to give oneself over body and soul to the worship and service of the Ruinous Powers either collectively as Chaos Undivided or individually as the Dark Gods may grant their more successful and powerful followers a favoured place within the Realm of Chaos upon their deaths. The most successful devotees of Chaos can even look forward to an existence as a Daemon Prince, a position of guaranteed immortality and control over one's own small demesne or Daemon World within the Realm of Chaos or a Warp Rift like the Eye of Terror.

The devotees of many variants of the Imperium of Man's Imperial Cult also believe that when a person dies, his soul is transported to the Warp. But a devout worshipper of the God-Emperor of Mankind holds that the Emperor protects his faithful within the Warp from all entities that might seek to harm them and gathers the souls of the faithful to himself. Only someone who has not been faithful to the Emperor and carried out His will or obeyed His commandments is at risk of being devoured by daemons of the Warp or otherwise punished within the Empyrean. In this way, the devotees of the Imperial Cult see the Warp as an analogue of the old Judeo-Christian concept of Heaven and Hell -- the Warp is Hell for those who have been unfaithful to the God-Emperor, but can become a form of Heaven for those who have been true to His will. Whether there is any truth to this belief is unknown, but the psychic nature of the Empyrean means that the collective and strongly-held beliefs of mortals in realspace tend to take on a reality of their own within the Warp. And there are a great many human beings in the galaxy, and a great many of them are fervent, even fanatical believers in the Imperial Creed. What is known with certainty is that those men and women of the Imperium who have displayed unshakeable faith in their concept of the God-Emperor have sometimes been able to enact feats that can only be considered miraculous by any fair use of the term. These feats have been particularly potent when deployed as weapons against the servants of Chaos, daemonic and mortal alike. It may very well be possible, that in fact, as the ancient credo tells us, the Emperor protects...

Warp Entities

The Warp, through a realm of pure psychic energy that is inimicably hostile to all forms of organic life from realspace, is home to its own forms of life, sentient and otherwise. Many of these creatures are not sentient but depend upon the absorption of psychic energies to survive and are thus naturally drawn to the psychic emanations of mortals in realspace whose psyches are the very wellspring of the Empyrean. Such creatures include the Vampire, Psychneuein, Astral Spectre, Astral Hound, and the hideous Enslavers.

Enslavers are spontaneously created by the shifting energies of the Warp from the nightmares of sentient species, and prowl the Immaterium like sharks. The Enslavers are able to psychically control other species, forcing them to their will, hence their name. Enslavers are able to control almost any species, even creatures such as Tyranids and daemons! However it is thought that the only race immune to the Enslavers are the Necrons, who have no souls nor psychic presence in the Warp. Enslavers exist primarily in the Warp, but can enter the physical universe like a daemon through the unprotected mind of a human psyker. They are able to do this when three Enslavers band together to form a 'trinity', whereupon they form a psychic bond with their psyker victim. Over the course of the next 2-3 days after contact is made, the psyker's organic chemistry changes significantly, the end result being a living, pulsing Warp Gate, through which the Enslavers travel into the material universe. Enslavers are rather like an octopus in shape, their main body being made up of two roughly circular parts, one on top of the other. They have 8-12 small tentacles protruding from their bottom half, and 2 larger tentacles ending in suckers. On the smaller, upper half of their body, they have a sensory organ sometimes referred to as an 'eye'; this circular organ is normally reddish in colour. Their leathery skin is able to change colour, but is normally a light brown with pale tentacles.

But far worse than these creatures are the truly intelligent denizens of the Warp, the Daemons of Chaos. Starships that travel through the Immaterium by use of a Warp-Drive are shielded from attacks by these creatures by their generation of a Gellar Field. Should this field's emitters fail or malfunction, the crew of the ship will be at the mercy of all of these horrors, and will likely be consumed by daemons or become their mortal playthings. The Warp is also the home of the greatest of all terrors, the four major Chaos Gods -- Khorne, Nurgle, Tzeentch and Slaanesh -- who each dwell within a separate kingdom within the Realm of Chaos, the existential embodiments of the darkest aspects of countless sentient species' psyches. Though the Immaterium and the Ruinous Powers are essentially composed of the same kind of psychic energy and the terms "Warp" and "Chaos" are often used interchangeably by those who are aware of the nature of the Immaterium within the Imperium of Man, each Chaos God maintains a primary form that embodies their nature and that is instantly recognisable to their legions of daemonic and mortal followers.


The Chaos Gods are not alone in Warpspace. They have created servants from their own essences -- the creatures that mortals have named daemons based on their ancient legends and religious mythologies -- who are not so closely bound to the Warp. Daemons are entities of a somewhat different nature to their masters, and are the most numerous of the creatures to be found in the Empyrean. A daemon is "born" when a Chaos God expends a portion of its own power to create a separate being. This psychic power binds a collection of senses, thoughts and purposes together, creating a personality and consciousness that can move within the Warp. The Chaos God can reclaim the independence it has given to its daemon children at any time, thus ensuring their loyalty. It is only though the loss of this power that a daemon can truly be destroyed, its mind dissolving into the whirls and currents of Warpspace.

Daemons have no physical presence within the Warp. The Realm of Chaos is anathema to the laws of physics and the starships that navigate its depths do so by taking a skin or bubble of "reality" with them when they enter using their Warp-Drive. Instead of possessing a true physical form, daemons project a form conjured from raw psychic energy that is essentially a lesser interpretation of their master's fundamental nature. Hence, the bizarre and inhuman appearances projected by daemons indicate their presence, status and allegiance to a Chaos God.

Though it may appear to be made of normal matter when it materialises in realspace, a daemon's form is no more physical than it is in the Realm of Chaos. In fact, they are beings of pure Warp energy given shape and depth. When manifested in the material universe, daemons have particular invulnerabilities and weaknesses, as well as many strange powers derived from their Warp-born nature as psychic beings. Slaying a daemon's physical projection does not kill it, but only severs its presence in reality; its true essence in the Warp remains unharmed.

When a daemon is "killed" in the material universe, it is banished back to the Warp. If not simply re-absorbed by its creator, it must remain there to regain its strength that it eventually might manifest itself again. Legend has it that a daemon banished in this way cannot return for a thousand Terran years and a day,, though it is of course impossible to prove such a belief through study, and the concept of time itself is meaningless within the Warp. The slight to a "slain" daemon's pride is considerable, however, and the daemon is forced to endure the mockery of its fellows until it can return to corporeal form and avenge itself. The most powerful daemons will call upon any servants and tributary Lesser Daemons to help them achieve their revenge. If it has many allies, it may also request their aid, though all daemons are cautious in doing so. Such favours must inevitably be returned, and no daemon welcomes the dominion of another creature, be it mortal or daemonic.

Daemonic Incursions into Realspace

Daemons strongholds

Daemonic strongholds in the Eye of Terror

In order for a daemon to break through into the mortal universe, there must be a breach of the barriers between Warpspace and the material realm -- a Warp rift (also see below). These are breaches in the fabric of reality that can vary in nature and size, such as the massive Eye of Terror or the Maelstrom. Sometimes these occur randomly; at other times, either mortals or the Chaos Gods themselves bring about their creation by some supernatural act. The size of the breach can vary tremendously, from a slight thinning of the dimensional walls to immense wounds in reality that allow the daemonic legions to invade en masse.

At times when certain conditions like the appearance of a Warp Storm or a sorcerous ritual have weakened the barrier between the Warp and realspace, a daemon can possess a mortal and turn him or her into a living portal through which whole daemonic hosts can pass for a time into the material universe. These daemonic incursions can taint realspace severely, often twisting and reshaping whole planets until they are lost into the Warp, becoming a part of the Immaterium and thus transformed into Daemon Worlds. It is not surprising that the Inquisition's Daemonhunters, the Ordo Malleus, are granted unlimited resources and political power by the High Lords of Terra to deal with such terrible threats to the continued existence of Mankind.

Often, it is the tumultuous movements of the Warp itself that create a break into the material realm, allowing daemons to spill through the resulting breach. This might happen by chance; events such as the onset of Warp Storms, Warp-Drive implosions or a rogue psyker's mind suddenly exploding with raw power can cause a rift to appear into the Immaterium. At other times, the deliberate rituals and blood sacrifices of Chaos-worshipping mortals can allow the teeming hordes of the Chaos Gods to smash through into the material realm. Sometimes, simple mortal suffering, death and misery on a massive enough scale can form a Warp rift that a daemonic legion might use as a portal. Some Warp rifts last mere hours, or even moments, for the nature of Chaos is ever impermanent. A daemonic army that has passed through such a rift can become trapped in realspace and will swiftly succumb to the constant leeching of the Chaos energy required to maintain its presence.

Of these, the greatest and most dangerous Warp rift is the Eye of Terror, which has lasted for more than ten thousand standard years. The Eye can be seen as a purple-red bruise upon the firmament from fully half the worlds claimed by the Imperium. It was created by the birth of the Chaos God Slaanesh in the early 30th Millennium and is home to unnumbered Daemon Worlds fought over by daemons and mortals alike, the infamous Traitor Legions of the Chaos Space Marines amongst them. Another Warp rift of excessive magnitude is the Maelstrom, found near the galactic core and a haven for thousands of pirates and Renegade Space Marine Chapters. Other, less widely known Warp rifts exist, such as the Heart of Darkness near to the world of Atilla, the Storm of Judgement that engulfs almost all of the Caradryad Sector, Hell's Gullet, which threatens to swallow the Berillian System whole, and the infamous Screaming Vortex that marks the border between the Calixis Sector and the frontier of the Koronus Expanse in the Halo Stars.

Random Warp rifts are often caused by Warp Storms -- roiling expanses of turbulence within the Realm of Chaos that are echosed in realspace, restricting Warp-dependent travel and communication. If they become focussed or powerful enough, they can pull the fabric of reality taut or even tear it open. Compeletely unpredictable, Warp Storms can be isolated to single planets or expand to encompass whole sectors. One of the worst Warp Storms ever recorded in human history cut Terra itself off from the rest of the galaxy for the entire 5,000-year-long epoch known as the Age of Strife. The unfortunate worlds in the vicinity of such a cataclysmic event can become the playgrounds of daemons until the storm finally expends itself. A few Warp Storms have endured for so long that they can be considered permanent, their self-sustaining energies trapping nearby planets and star systems in a quagmire of roiling Chaos.

Without the Warp, there would be no psykers, no interstellar travel and no interplanetary communication. In fact, the Warp is essential to the survival of humanity. Spacecraft travel through its shifting tides, capable of travelling thousands of light years in a fraction of the time a journey using conventional reaction drives at sub-light speeds would take. By such means, humanity is bound in a single interstellar Imperium, led by the divine Emperor of Mankind.

Through astrotelepathy and the guidance of the psychic mutants known as Navigators, the worlds of the Imperium are able to maintain their fragile bonds. The Emperor's will may be mighty, but His reach is long only because His fleets can travel through Warpspace, the fragile bubbles of reality that protect each warship held up by complex Geller Fields and raw faith.

While Mankind would have a fraction of its current numbers and strength without the Warp, Chaos in its turn would be much diminished without the presence of humanity in the galaxy. The Chaos Gods drink emotions and thoughts, growing bloated with psychic power in the process. Over the millennia, each has fed on an aspect of human nature: rage, desire, corruption and inconstancy. Strengthened and moulded by the collective thoughts and emotions of the inhabitants of reality, the Dark Gods nurture in Mankind those same passions that sustain their very existence. As humanity has spread across the stars, its numbers have grown immeasurably, fuelling the Chaos Gods. So the circle is established, with mortal follies and weaknesses feeding the Dark Gods and those same gods then encouraging Mankind in turn to further follies and weakness.


A lone Space Marine confronts a hellish daemonic incursion into realspace

Humanity has long been able to use the power of the Warp -- magicians, seers, witches, mediums, shamans and exorcists have all trapped into its power across the breadth of human history, albeit often unwittingly. Psykers such as these manifest their powers by drawing upon the Warp, siphoning its unnatural energy to hurl blasts of energy, teleport objects, send their thoughts across space and time and perform countless other "miracles." Once, the gift of true psychic power was confined to only a few helpless individuals who usually fell victim to superstitious prejudice in Mankind's distant past. However, the number of psykers is rising in the galactic population of humanity with every passing century. This constitutes a profound evolutionary change for Mankind. Every time a psyker draws upon the Warp, he disturbs its natural flow, creating an eddy that may simply die away or be fed by other movements until it becomes a raging tempest that feeds a Chaos God. Each psyker causes a pinprick of disturbance within the Warp; each can be the seed of a Warp Storm; each can rouse a Chaos Power to unthinkable conquest.

The invasion of a daemonic army is analogous to hell being unleashed upon reality. Free from the physical limitations of a mortal force, a daemonic legion can appear and disappear at will. On occasion, it will mass for a great attack; at other times, individual packs of daemons will hunt across the affected globe, terrorising the populace, randomly enslaving and killing. Those mortals with even the least psychic potential suffer first as the influx of Warp energy releases the latent power of their mind, immolating them with magical fire, turning them into rocky statues, or causing their brains to simply explode. Poltergeist activity and random brusts of pyrokinesis can ruin buildings in an instant. People hear deranged screams and lurid whispering whilst unnatural stenches taint the air.

A daemonic invasion is all but impossible to stop by conventional means, for the very act of warring against daemons feeds the psychic power keeping them in realspace with fear and hatred. Only the closing of the Warp rift can deprive the daemons of their power. Often, there is nothing that can be done but battle against the incursion until the Warp rift runs its course. Battles fought against a daemonic incursion are utterly different than those against mortal foes, for defensive structures and garrisons have little to no effect. To wage war against invading daemonic hosts, an army must be ready to respond to the most sudden appearances of its adversaries.

To compound matters, the motivations behind daemonic incursions are unfathomable. Even the Tyranids, who are so alien as to be beyond the ken of man, war for sustenance and survival. Instead of these base drives, the objectives of a daemon commander will often be completely obscure -- they might be to slay a million mortals, to retrieve a single artefact, or to kill the grandchildren of those that once banished them back to the Warp. Other times, the Daemons have no goal or plan at all, and the gibbering creatures of the Immaterium make decisions according to opportunity and their intrinsic nature.

To fight a daemon army is to fight a twisting tornado of unreason and despair. Even then, the Imperium cannot allow the knowledge that such foes actually exist to spread. The human survivors of such conflicts are invariably confronted by the Inquisition and mind-wiped, quarantined in forced labour camps or even -- in extreme cases -- become the subjects of a worldwide Exterminatus event. Over the aeons, the galaxy has witness Warp-based catastrophes and daemonic incursions beyond counting. Since the inception of the Imperial Inquisition in the early days of the Horus Heresy, even the fact that such a thing is possible is deemed too dangerous for the citizens of the Imperium to know, for such knowledge breeds heresy as surely as a flyblown corpse breeds maggots. because of this, the vast majority of knowledge concerning daemonic incursion has been eradicated from extant Imperial public records. What is known is recorded only in proscribed Imperial texts and heretical xenos scripts that the Inquisition has yet to destroy.

Warp Rifts

On rare occasions, the realm of the Immaterium is able to break out into the physical universe in what is known as a Warp Rift. A Warp Rift is a weakening of the barrier between realspace and the Empyrean, allowing its creatures to enter the material universe. Sometimes, Warp Rifts occur randomly, while other times, the Chaos Gods or mortals manufacture them. Some last mere moments, others for days, years, or even for Terran centuries. They can take many forms, often a seething whirlpool of raw psychic power, other times as a terrifying glimpse into the Realm of Chaos. They have also appeared as gates of green fire, clouds of impenetrable shadow, boiling lakes of pus, and other terrifying visions capable of driving mortals mad. These Warp Rifts are usually settled by the once-mortal followers of the Ruinous Powers of Chaos, and are often the site of titanic atrocities previously unleashed in the local region of space by these Forces of Chaos.

A number of different factors can induce the formation of a Warp Rift in realspace, including the unpredictable movements of the Warp causing a break into realspace, the daemonic possession of a mortal, deliberate rituals of daemon summoning carried out by Chaos Cultists, a breach in the barrier between realspace and the Warp caused by the psychic focus of immense suffering and death following a great war or terrible atrocity, a Warp-Drive implosion, or as a result of the unified will of the major Chaos Gods.

The most well-known Warp Rifts in the Milky Way Galaxy include:

Warp Storms


A dreadful Warp Storm corrupts an unfortunate world

The Warp is an extremely volatile medium. At times, disturbances can turn areas of the Warp into raging storms of incomprehensibly destructive fury that can breach the barrier into realspace. These storms can last for days, months, or even standard centuries. These "Warp Storms" can isolate star systems and entire sectors from each other, by making the Imperium's normal methods of interstellar travel and communication impossible as the Warp surrounding those regions becomes too chaotic for a starship to safely travel through or for an Astropath to send or receive a telepathic message through the psychic "interference." These storms can last for any amount of time, ranging from weeks to centuries, and can occasionally break out into the material universe, creating a temporary Warp Rift that can result in an incursion by the Forces of Chaos into Imperial space. Starships caught in these storms are likely at best to be driven far off-course and emerge back into realspace thousands of light-years from their intended destination in uncharted areas of the galaxy. More often, such vessels find themselves trapped within the Warp, a terrible fate for its passengers as they become playthings for the dark creatures that inhabit that malign realm when their protective Gellar Field finally fails. While uncommon, some starships, after making their way through the Empyrean for only a short time, will emerge from the Warp only to find that entire Terran centuries have passed in realspace. Such an occurrence is more likely to happen when a vessel is travelling through a region of the Warp affected by a Warp Storm or unusual psychic turbulence. However, the Warp is a dangerous and chaotic place at the best of times; every use of a Warp-Drive is perilous, no matter how routine.

Controlling the Warp

There are conflicting accounts as to whether it is Tzeentch, the Emperor of Mankind, or a creature known as the "numan" (from the Inquisition War Trilogy) that prevents the Immaterium from spilling out and completely engulfing the material universe. However, recent canon seems to imply that the anti-psychic technology of the Necrons contributes, too. It is also possible that the laws of physics act as a barrier. It should also be noted that the Immaterium seems to only be relevant to the Milky Way Galaxy (although the Tyranids' case poses a question), implying that it is either a unique occurrence, that there may be other "Warp shadows" of other galaxies where sentient life exists or that the Warp continues in other areas, but uninhabited by daemons due to the lack of sentience. A paradox of thoughts is apparent: the extra-dimensional entities of the Warp are sustained by the minds and souls of living creatures within the physical world. So what would occur to the Warp if all life was obliterated through the fall of the physical reality? It would probably cease to exist.


  • Codex: Chaos Daemons (6th Edition), pp. 6-20
  • Codex: Chaos Daemons (4th Edition), pp. 6, 8-9, 14-16, 25, 44
  • Realm of Chaos: Slaves to Darkness (1st Edition), pg. 212
  • Rogue Trader: Core Rulebook (RPG), pp. 310-313
  • The Horus Heresy - Book Two: Massacre (Imperial Armour), pg. 27
  • Warhammer 40,000 Rulebook (6th Edition)
  • Warhammer 40,000 Rulebook (5th Edition)
  • Warhammer 40,000: Rogue Trader (1st Edition), pp. 130-132

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