Psyker

Psykers are individuals with psychic abilities. Psykers draw their powers from the Warp, and hence are often in danger of daemonic possession and insanity.

Psykers of Different Races
Most races in the Warhammer 40,000 universe employ some form of psykers to their use on the battlefield; some are inevitably more potent than others. There are two exceptions to this: the Tau and the Necrons. The Tau have yet to bear any psykers and Necrons have zero contact with the Warp as a whole.

The Imperium of Man
Psykers, although justifiably feared throughout humanity, serve several vital roles within the Imperium.

Psykers are too dangerous to remain at liberty; their minds are susceptible to daemonic possession. Uncontrolled, they can intentionally or unintentionally cause the destruction of entire worlds. Humans found to be bearing psychic mutation, if they are not simply killed, are sent to Terra aboard the infamous Black Ships which endlessly traverse the Imperium.

All human psykers have an ordained role as servants of the Imperium. The exact role depends on their psychic power and their strength of character.

Psykers serve within the Imperial Guard and the Space Marine Chapters, employing their powers in battle as well as for civil duties. Navigators are required to cross safely through the Immaterium. Astropaths provide faster than light communication. Thousands of psykers are sacrificed to sustain the Emperor, and thousands more must constantly be drained to power the Astronomican, which broadcasts an enormous signal through the warp which is used as a point of reference by ship Navigators. However, the Imperium of Man also executes countless psykers as they are seen as mutants, potential threats, or gateways to Chaos.

Astropath Origins and Role
Astropaths (short for astro-telepath) serve throughout all the Imperium's divisions and make up a communication network designed to transmit and receive psychic messages through interstellar space.

They are chosen from the multitudes of psykers brought to Holy Terra on the Black Ships due to their great power. Once chosen, Astropaths receive psychic training by the Astra Telepathica's teaching division which is known as the Scholastia Psykana, before they are "soul bound" to the Emperor. This ritual transfers some of the Emperor's vast power to the psyker. Such an experience is traumatic for the psyker and not all survive or maintain their sanity. Even the survivors suffer damage to their physical senses, especially their eyes, so that almost all Astropaths are blind. Their increased psychic senses however tend to make up for this loss of sight.

Being joined with the Emperor is necessary however, as it greatly heightens Astropaths' already formidable powers, giving them the ability for which they were chosen - to transmit and receive psychic messages across large distances of space.

Due to the draining nature of their job many Astropaths are physically frail and can die quite young through exhaustion.

Imperial Guard
Some of the psykers recruited into the Adeptus Astra Telepathica are trained to serve within the Imperial Guard as Sanctioned Psykers. These psykers may draw upon the power of the warp, unleashing it upon their enemies. They are also called upon to advise high-ranking officers, with varying degrees of success. Their limited training and equipment leads to them being more easily preyed upon by the perils of the Warp than perhaps the much more powerful Librarians of the Space Marine Chapters. Each time they utilise their power, they put themselves at considerable risk and are prone to have their minds destroyed in the process. Some Psykers in rare cases have even literally exploded from overloading their bodies with warp energy, taking out entire squads nearby. That aside, they are still a potent force when deployed and used properly. On the battlefield, Sanctioned Psykers can advise an officer and guide their command, protect him from psychic attack, or fire bolts of lightning from their hands.

Outside of the tabletop game, Imperial Guard Sanctioned Psykers appear in the video game Dawn of War as members of the Imperial Guard faction.

Space Marines
Psykers are employed by the Space Marines in the form of Librarians. These individuals are chosen from among the most powerful psykers. Librarians are responsible for maintaining the records of the Chapter they belong to, and can also use their talents to divide psychic mutants into those that are dangerous and those that can be utilised by the Imperium. Librarians, having much better equipment (aegis hood circuitry etc), willpower, protection and training, combined with the enhancements of a Space Marine are much less prone to the perils of the Warp than other Imperial psykers.

On the battlefield, Librarians are fearsome opponents, able to unleash devastating psychic powers and augment their own physical prowess. They are also skilled at defending themselves and their battle brothers from psychic attack.

The Inquisition
Though they are tasked with hunting down rogue psykers and collecting latent ones for training to aid the Imperium, many inquisitors are psykers themselves, Inquisitor Gideon Ravenor being an especially potent example. Like much of their organization, one inquisitor's psychic abilities can vary greatly from another's. Some specialise in unleashing torrents of fire while others, like Inquisitor Gregor Eisenhorn, specialise in powers that aid them in interrogations or to fool an enemy into stepping out from cover, dropping his weapon, or any number of other subtle 'mind tricks'.

Grey Knights
The Grey Knights Chapter is wholly made up of psykers: being a psyker is a condition for recruitment. Due to the entire chapter being psykers the rigorous selection of becoming a Space Marines is increased all that much, with all selected battle-brothers having no memory of their past and many falling before gene-seed implantation can be complete. What is amazing is that, despite the entire chapter being comprised of only Psykers, not one Grey Knight has ever turned to Chaos.

Eldar
Among all the races, the Eldar possess some of the most powerful psykers, using their ability to divine the future to shape their fate and also unleashing devastating powers on those that oppose them, however the sheer power they generate combined ensures that they must be cautious unless they attract the attention of Chaos and so are forced to become highly disciplined and regulated in psychic usage. Eldar Psykers come in the form of either Farseers or Warlocks, the former being the more powerful. Farseers will lead the Eldar warhost against the enemy and shape the course of battle with their powers. Warlocks are typically bodyguards and possess lesser, normally defensive powers. The Ulthwé Craftworld is said to possess the greatest number and the greatest quality of Eldar Psykers, due to its proximity to the Eye of Terror, and they can divine much further into the future and with better clarity than that of other craftworlds. The Craftworld Iyanden has a variant of Warlocks, called Spiritseers. They differ very little from their normal counterparts. Spiritseers can guide Wraithguard in combat, better directing their awesome firepower for optimum efficiency.

Legions of Chaos
The forces of Chaos host a great many mutants among their number. Chaos psykers can perform various tasks such as summoning daemons and unleashing devastating powers upon the enemy. The Chaos God Tzeentch is devoted to sorcery; legions worshiping Tzeentch such as the Thousand Sons possess a large number of psykers that can aid in battle. Other legions such as the World Eaters denounce magic and psychic ability in favour of the wanton bloodshed of close combat and the Iron Warriors often sneer at sorcery. Chaos sorcerers can unleash potent powers and are fearsome individuals, but are often mutated beyond recognition. Tzeentch Sorcerors are especially potent, able to perform feats that would leave a Farseer speechless.

Orks
All Orks' are relatively powerful latent psykers, however they do have true, active psykers known as Weird Boyz. Ork psykers differ from those of the other races in that they don't draw their power from the Warp, but instead from the latent psychic powers that all Orks have. The Weird Boyz then channel this Waaagh! energy to inflict damage upon their foes, but often end up killing themselves in the process.

Necrons
The general belief is that Necrons do not have Psykers, as they are little more than robots, and are described as having virtually no souls; meanwhile, C'tan are described as considering warp energies to be "anathema". The Necrons also are notable for utilizing technology specifically designed for destroying psykers, specifically the "pariahs". However, some contradictory evidence comes from the novel Caves of Ice, in which the Necrons emit a fear inducing telepathic ability, from which the unlikely hero of the novel, Ciaphas Cain is saved only because of the presence of a "psychic blank" in the vicinity. Possibly this is a deliberate ploy by the author, emphasising the limited knowledge and conceptions of the book's characters (compared to the relative 'godlike' knowledge of a reader well-versed in Warhammer 40,000 lore), using what terms they know to rationalise what they experience however ultimately inaccurate they may be.

Tyranids
The alien race of the Tyranids is one of the most psychically active races in the galaxy, if not the most, with every single tyranid telepathically connected to all others in what is called the Hive Mind. It is suspected that this constant and massive "psychic traffic" is what causes the Shadow in the Warp, a phenomenon that makes warp travel and astropathy almost impossible near a large tyranid fleet. Though the lesser creatures have no psychic abilities of their own, the larger tyranid warriors act as focal points for the Hive Mind, capable of mind-controlling all lesser tyranids around them. Zoanthropes, creatures supposedly evolved by combining tyranid DNA with DNA from other psychically active races like the Eldar, are extremely powerful psykers to the point that, with the passing of the years, their bodies have devolved into little more than a humongously bloated head attached to an atrophied, fetus-like body incapable of even moving on its own power, therefore requiring for the creature to use its psychic abilities to levitate across the battlefield. Hive Tyrants are also very powerful psykers, although not as much as Zoanthropes, and act as the core of the Hive Mind within the tyranid swarms. Larger tyranids, such as Dominatrixes and the mysterious Norn Queens, are also psykers of immense power, though the full extent of their abilities is a matter of speculation.

Tau
Tau have no known psykers. In the video game Warhammer 40,000: Fire Warrior, it is revealed that the Tau are naturally resistant to the mutating effects of Chaos, having almost no psychic presence in the warp at all. However, this does not prevent the Tau Ethereal, Ko'Vash, being blasted apart by a burst of Chaos energy. It is rumoured that the Ethereals are capable of utilising warp power, as it is suggested that this is how they are able to cause such loyalty in all of the Tau, although it was suggested in the Warhammer 40,000 book, Xenology, that the Ethereals have a large scent-based organ in their head that allows them to control other Tau through pheromones.

Psyker Levels
There are different grades regarding the power of a psyker:
 * Alpha Plus
 * Alpha
 * Beta
 * Gamma
 * Delta
 * Epsilon

...and so on down the Greek alphabet. After alpha plus a reverse chart begins all the way to omega plus. Only a chaos god can claim such power.

The power the top four grades represents is immense. A high Delta level can read the minds of a good sized town simultaneously, or crush a man to death against a wall in seconds. High grade psykers are extremely powerful, and not to be taken lightly. Beta level is the highest a human can go and still be considered sane.

An Alpha Plus, however, is a being of grotesque power. They are described in the 4th edition Rulebook as being able to "turn a man inside-out with a glance", "snap a Battle Titan in half with a flick of the wrist", and "a muttered syllable can turn an army upon itself in a frenzy of blood lust". They are capable of destroying entire worlds - sometimes unintentionally.

There is some controversy as to whether this description should be taken as an objective description of the Alpha Level of psychic mastery, or if it is intended to be read as Imperial propaganda, and just being the exaggerated view of the generally anti-psychic authorities of the 40K world. In Dan Abnett's works, where the term first appeared, the Alpha Level psyker Esarhaddon (also the name of the King of Assyria between 681-669 BC) is powerful and able to control hundreds of Imperial citizens as puppets against the protagonists, but he is not described as being powerful enough to destroy a battle Titan, and is eventually subdued.

However, there are very few Alpha or Αplha Plus psykers that can be controlled safely, or even at all. Because more powerful psykers attract proportionally more interest from warp-bound daemons, many are driven insane, tainted by Chaos, or even become possessed (examples include the Apex Twins, who were responsible for murdering scores of Imperial Regiments). They are one of the biggest threats the Inquisition has to face, and are the reason that the Ordo Hereticus was formed. Most are executed, as the threat they pose is simply too great to deal with or control in any large degree. Ravenor in Dan Abnett's Ravenor Rogue is confirmed to be a Alpha Plus psyker towards the end of the book.

An example of a Beta level psyker is Sergeant Agun Soric, an Imperial Guardsman from the Gaunt's Ghosts series of novels by Dan Abnett. He is able to detect blood poisoning in a fellow trooper, but his most prominent power is his ability to write messages to himself, which are contained in a brass message shell. Even after throwing the shell away, he would soon find it wriggling in his pocket, containing a message written in his own handwriting. At first the messages contained advice or warnings, but soon began to include criticism as he began to realize what he was, and the danger he posed as an untrained psyker. He is eventually discovered and taken by the Inquisition's Black Ships. His ultimate fate remained unknown for several novels until "Only In Death", where he is discovered by Commissar Viktor Hark.

In Ian Watson's novel Space Marine, an individual's psychic profile is represented by a decimal value, presumably from 0 to 1, instead of using the Greek alphabet system.

Anti-Psyker Weaponry
Several types of anti-psyker weaponry have been developed by the Imperium, Necrons and other races to counter psykers. For the Imperium, these include the Culexus Assassin and their psykout weapons, which have devastating effects on psykers. Weapons include psycannon, warp swords, and other psykers. Necrons have developed several Pylons that, once complete will completely separate the warp from the material universe, thus rendering psykers useless. On a smaller scale there are the Pariahs, Necrons made from humans with the pariah gene - this makes them, like the Culexus assassins, soulless, and severely debilitating to nearby psykers.

Lastly, the Dark Eldar, while not having any known psykers among their ranks, have developed weapons designed for psyker destruction. One of the most gruesome (and rare) is the Crucible of Malediction, a nightmarish device which contains the essence of a slain psyker tortured into insanity. When the Dark Eldar use this weapon, the psykers tormented soul is released and its power has the potential to consume any psyker on the battlefield.

Notes and references
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