Psyker

Good thing Games Workshop has an extremely liberal interpretation of the word 'psychic'. Magic IN SPEHSS!

“We always vilify what we don't understand.”
- Nenia Campbell

A psyker, in the Warhammer 40,000 universe, is an individual with psychic powers capable of accessing the Warp. This is both a blessing and a curse; though psykers are often able to achieve spectacular feats with their abilities, the Warp is a perilous place, and whenever a psyker uses their abilities there is a chance that they will be subject to the Perils of the Warp. Death is one of the milder results of this; extremely unlucky psykers might actually be raped in countless ways by daemons and used as a gateway from the Warp into the physical world. Luckily, in the ranks of the Imperial Guard, where there's a psyker, there's usually a Commissar ready to unleash the power of Blam.

Types of Psyker

The different races of the setting perceive psykers in different ways.

Imperium

The Imperium of Man regards most psykers as extremely dangerous, because these are people with scary powers, and the influence of the Warp tends not to let them stay sane for very long, but hey, space wizards are cool. There is also the threat of Chaos possessing them and summoning daemons. Thus, the Inquisition hunts them down so they can either be sacrificed to feed the Empra or sanctioned and made to serve the Imperium (under an inquisitor's watchful eye). Such psykers appear as a unit in the Dawn of War games and like to scream incomprehensible one-liners so mind-numbingly loud that they may very well actually make your head explode. Space Marines make their psykers into Librarians: in addition to psychic support on the battlefield, they compile records in the Librarium, serve to assist in battlefield communications, and test their brothers for Chaotic contamination. Imperial Guard Sanctioned Psykers combine psychic powers with Standard Issue Balls of Steel that every Imperial Guard member has. In addition, they have a nasty reputation for being BLAMMED by Commissars. "Rogue Psykers" is the official designation for any psyker who hasn't been collared by the Imperium yet and are often hated by more puritan worlds, in extreme cases routinely being hunted down and killed; but on most worlds being sactioned (assuming you survive and don't mind the side affects) gives an air of authority and orthodoxy to an otherwise hated thing. People still hate you, but instead of treating you like a particularly verbose bit of dung, now you're hated the way tax collectors are hated. Astropaths are beyond such venom, partly because they are less prone to possession and mostly because they are a planet's only way of communicating with the greater Imperium. People still feel uneasy around them, but even Black Templars have to cope with them and make nice faces. Pointing out that the Emperor was a psyker usually results in the person struggling to make a retort for a few moments before beating you to death. Well, actually not, since for an average citizen of the Imperium the Emperor is God, so His wielding godly powers in the glory days before His ascension is actually the core tenet of the Imperial Cult and proof of his divinity. Not so for mere mortal psykers, who are rightly considered unholy and corruptible.

Humanity being the stars of the show obviously have arguably the greatest psychic potential overall (because of course they do), with a psychic evolution (which could take countless centuries or even millennia to take place; even if they can survive it) into a full psychic race which the Emperor himself has said may very well equal or even possibly surpass even the Eldar at their peak, although with the loss of the Webway project even the Emperor admits that this path is pretty much now closed to humanity. Becoming a psychic race doesn't suddenly make you god tier, it just makes you psychic; the Eldar are a full blown psychic race and they aren't exactly doing brilliantly.

Humanity has managed to produce amongst some of the strongest Psykers in the history of the Galaxy but most didn't come into being through natural means:

• The Emperor is obviously the first that springs to mind as he is unquestionably the strongest mortal psyker that has yet been seen, unless you count the Old Ones. The question is however: is he even human? There are many theories surrounding the Emperor's origins and his exact nature. Was he born or is he a construct from the Dark age of technology that believes itself to be human? If we take the whole Shaman origin as fact then his psychic might is due to the large number of psychic beings merging their minds into one which is certainly not the norm (strangely something similar happened to Ephrael Stern). Even if we assume he's a single entity that happens to be immortal, there is the whole deal with the Chaos gods which may or may not have boosted his already considerable power. The Emperor is clear proof that, whatever he might be, the most powerful psyker in existence has indisputably allied itself with humanity.

• Magnus is a Primarch and should in no way be considered entirely human. He, like all his kind, are artificial beings created through Warp shenanigans and advanced bio engineering. There is nothing natural about him or his psychic might.

• Malcador is the only truly natural (depending upon what happens with his back story once it is finally revealed) human standout amongst the big names. He may play second fiddle to the likes of the abominations that are the Emperor and Magnus but he is still the strongest "human" psyker on the list. Natural humans are never going to be able to compete with the gods of the Warp, but a race of potential Malcador's doesn't sound too shabby now does it.

Human psyker types in 40k:

Psyker type	Description	Image
Navigator	Not really Psyker but strange enough to make the list	Weirdos
Astropath	Probably the most common type of psyker in the Imperium.	Definitely the best looking human psykers
Sanctioned/Wyrdvane Psykers	Poor Bastards	Can you hear the voices too?
Primaris Psykers	The best human non space marine psykers in the game
Grey Knights	All have some Psychic powers, but nowhere near a trained Librarians level. Epimetheus- one of the original Grandmasters, currently captured by Chaos as a potential vessel for slaanesh. Kaldor Draigo Grand Master Voldus like many Grey Knights and even other Space Marine Librarians, Voldus and his predecessors have often performed feats far beyond that shown by any Eldar Farseer, with Voldus, in the crunch on the table top, actually having basic net superior abilities to even Eldrad. Brother-Captain Arvann Stern Castellan Crowe
Librarians	The most powerfull psykers at the Imperiums disposal Lexicanium (level 1 Librarian) Codiciers (level 2 Librarian) Epistolaries (level 3 Librarian) Chief Librarian (level 4 Librarian) Varro Tigurius (Ultramarines) is arguably the greatest human precognitive in the galaxy, with accurate predictions and manipulations which put Farseers to shame (like that hard to do), and the only Psyker to possibly make contact and read the mind of the Hive Mind itself and survive, using that knowledge against the Tyranid. Mephiston (Blood Angels) Njal Stormcaller (Space Wolves) Ezekiel (Dark Angels)
Librarian Dreadnoughts (Blood Angels)	Armoured psychic coffin
Inquisition	Don't mess with these guys Inquisitor Greyfax Inquisitor Coteaz	Oh look, i've stepped on something. It's your face

Forces of Chaos

Chaos tends to have...varied opinions on psykers.

• Daemons are made out of the stuff of the Warp, and using psychic powers is shaping and throwing out a little bit of the Warp; so a daemon using psychic powers is the rough equivalent of taking a severed limb or some bones and throwing it as a viable attack. While that sounds pretty fucking metal, Khorne thinks that pulling this bullshit is a sign that you're not manly enough to get into the thick of it and handle the situation on your own. So it's an opinion shared by his daemons and his mortal followers. Not only do they not use psychic powers, but they actively hate any pussified deadbeat who uses them, and they even get toys that fuck with anybody trying to use those powers. However, it should be said that Khornate traitor librarians exist. Librarians by nature are beings that focus on destruction with their minds, so Khorne recognizes that as inner strength and makes an exception for them.
• On the other end of the spectrum, Tzeentch, being the god of magic, is hugely into psychic powers, and he likes making new ones that do all kinds of mix-and-match effects, though only the best are actually rolled out. That's the official line. He's actually a closeted pyro, and a lot of his powers are burny or...do weird shit. Being the patron of psykers, if people get Tzeentch's attention because they're scholars or David Xanatos, they'll eventually develop psychic power whether they like it or not. Due to higher exposure to Warp energy via psychic powers and serving the god of change, Tzeentch's minions, and more often, their minions have the highest rates of mutation and turning into Chao--er, tentacly gribblies. Ahriman, possibly the greatest of Tzeentch's Servants barring Magnus himself, was so powerful a Psyker that he was able to defeat Ulthwe's most venerated Psyker; Kyaduras the Anchorite, with ease and, in the same battle, also casually defeated Yvraine, the Yncarne and the Visarch.
• In the middle, Nurgle likes any psykers that spread his gifts around but doesn't really go out of his way to promote them in his followers either, probably on account of his direct opposition to Tzeentch. Needless to say, his powers all revolve around inflicting people with horrible diseases or boosting their endurance to unnatural levels.
• Similarly, Slaanesh thinks Tzeentch is a giant nerd, whose overdevotion to his nerdy hobby of inventing new psychic powers will never get him laid. We think it says this because Tzeentch refuses to sleep with it (it almost certainly likes his tentacles and crotch mouth) he's afraid he might catch Warp chlamydia, and he's just not willing to give Nurgle that kind of satisfaction. Slaaneshi psykers emphasize powers that makes the hurt feel good, or has effects that look like the target might have snorted the psychic power off of a stripper's ass.

Chaos psyker types in 40k:

Psyker type	Description	Image
Chaos Lords	Your soul may be damned, but at least the perks are good... I think Huron Blackheart
Chaos Sorcerers	Mixing psychic powers and sorcery, these guys are guaranteed to ruin your day
Followers of Tzeentch	Herald of Tzeentch Horrors Scarab Occult Sorcerer Aspiring Sorcerers Exalted Sorcerers Azhek Ahriman Kairos Fateweaver The Changeling
Followers of Nurgal	Typhus Malignant Plaguecasters Herald of Nurgle
Followers of Slaanesh	Herald of Slaanesh
Daemon Prince of Tzeentch, Nurgle or Slaanesh	With the backing of the Dark Gods, these guys are truly nightmares made real Be’lakor
Greater Demons	Lords of Change Great Unclean Ones Keepers of Secrets
Demon Primarchs	Magnus the Red Mortarion

Eldar

The Craftworld Eldar are a strongly psychically-attuned race (to the point as to a good chunk of their biology can't funcion were it not for their psychic power). While the regular, off-the-street Eldar will restrain themselves from using any psychic powers beside basic telepathic communication and the ability to use their psychic technology out of fear of being mindraped by Slaaneshi daemons, they can join the Path of the Seer and train to better control their innate abilities. Eldar who go on this path with previous experience as Aspect Warriors become Warlocks, while the most powerful seers can become Farseers and leaders of their people. They're ridiculously powerful psykers because of that deep imprint in the Warp to draw power, combined with their Spehss Ehlvan minds and willpower. They just need to be fucking careful and avoid unwanted attention unless they like tentacles.

Harlequins are also psychic, which really comes out in their shows, and although only the Shadowseer can use powers in a fight, other Harlequins do enjoy the benefits of psychic senses and silent telepathic communication.

The true capacity and depth of Eldar psychic abilities tends to be rather watered down or just plain ignored outright, due to the demands of the plot which is almost always told with the Imperium as the protagonist of the story. Within most stories the authors will tend to use the "M. Night Shyamalan" style of writing, which means having the Eldar Farseers getting a vision of events that are going to happen in the future and set out to stop it, only to discover that they either had it wrong the whole time ,or they themselves bought about the very event that they wished to prevent; all the while the authors are hopping around shouting "WHAT A TWIST" at the top of their lungs. Due to the vast focus put upon the forces of the Imperium it is not a surprise that there are so many named human Psykers present in the list below but remember that humans only produce an exceptional psychic individual once in a blue moon; those humans that prove themselves strong and stable enough to join the ranks of the Marines as Librarians are a rare breed but more then prove their worth over multiple centuries of service, so most if not all of the human Psykers of note will be present within the list below.

In comparison every Eldar citizen can, if they wish to, potentially become a Farseer; although no Farseer will ever manage to reach the same level of power as the likes of Magnus it's not really a fair comparison as he really isn't human and did not come into existence through natural means. Although it should be noted that although the likes of Spiritseers who are able to commune with and manipulate the souls of the Eldar dead the Ynnari actually amplify their existing powers through absorbing the souls of previous Eldar. GW's "fuck what the Xenos are supposed to be able to do; the Imperium and Chaos are the stars of this setting" rule is seen many times in the story itself, with powerful Eldar Psykers like Eldrad very rarely performing impressive feats within the stories they are featured in, and you are just told that they are very powerful before they are inevitably defeated by the glorious human protagonist (Loyalist or otherwise). Eldar Farseers, in particular, suffer from the "worf effect" more then most, despite often being heralded as great seers they have a terrible track record within the story line itself, very rarely succeeding in any of their endeavours. An important thing to keep in mind is that The Black Library writers love to add their very own super duper special human snowflake Psyker into the story because the "Rule of Cool" demands it, with many in the lore being attributed with the ability to destroy Titans and armies. Farseers on the other hand are often shown being incapable of even defeating a single Space Marine, let alone a tank, army or Titan, and Farseers are, explicitly, meant to be the most powerful Eldar Psykers in the galaxy. However, this could simply be either a way of keeping it so they don't win by default due to knowing exactly how a battle will go or (much more likely) Black Library incompetence making it impossible to get a remotely accurate depiction of what their powers can do.

The 8th edition codex seems to have made the attempt to address this situation. Whilst all Eldar walking upon the Witch Paths are capable of mastering many different physic disciplines throughout their long lives, they tend to avoid developing their more destructive powers, instead focusing all their efforts on developing their more “helpful” and “creative” powers; such as the Bonesingers, who use their powers to create and then craft Wraithbone. This goes well with the Craftworlder’s mindset when it comes to avoiding their darker more destructive sides.

Those who find it easier to master the more destructive disciplines tend to be those who have walked the Path of the Warrior and have already had their more violent impulses tested. These individuals will become Warlocks, and can make use of their more destructive powers upon the battlefield without putting those around them in danger; as they already have their War Masks in place, to help focus them and to separate their warlike selves from their normal selves.

Farseers will unfortunately still suck in any story that they are featured in, but they are not supposed to be just weapons, they are guides and advisers who help guide the blade, not swing it themselves. This, of course, doesn’t help the fact that they are still going to be treated like a bunch of red shirts, that will inevitably fail at every single opportunity by the writers at GW.

The Eldar make use of Rune Stones that act as conduits through which they can manipulate the psychic energise of a the Warp without actually having to interact with the Warp directly; though this does limit their overall psychic power level it does provide them with a much safer and controlled way to access the energies of the Warp. The Rune stones also act as psychic fuses burning out and cutting the link to the Warp should an Eldar try to tap into too much power before they are ready. As they develop their control and skill the Eldar psykers will eventually be able to use a far greater number of stones, which allows them to tap into far greater pools of power.

Eldar psyker types in 40k:

Psyker type	Description	Image
Eldar	Make use of basic psychic ability’s, but do not develop them in any meaningful way
Corsair Void dreamers	Void Dreamers serve as helmsmen and Navigators of Corsair ships
Exodite Worldsingers	Exodite psykers who make use of the power of nature, basically super druids
Harlequins Shadowseers	You like to mix psychic powers and hallucinogenic drugs, well your in good company Sylandri Veilwalker
Bonesingers	Eldar engineers and construction workers
Warlocks	Eldar Warrior psykers
Spiritseers	spooky spirit psykers Iyanna Arienal, the Angel of Iyanden.
Farseers	The de facto leaders of the Eldar Craftworlds, they help steer the Eldar race towards a more prosperous future... or get everyone killed; after they get it all wrong once again Eldrad Ulthran Macha, from the Dawn of War games. Taldeer, from the Dawn of War games.
Wraithseers	Psychic Wraithlord
Ghostseers	Psychic Wraithnig... oh fuck it
Hemlock Wraithfighter	Psychic plane. Oh come on this is getting ridiculous, whats next, Psychic mopeds
Warlock Titans	It's exactly what it says on the tin, a fucking Psychic titan. As a side not, one of these things kicked Sanguinius arse during the great crusade, sending him and his entire legion off to sit on the sidelines, watching as mere spectators whilst it and the Ordo Sinister battled it out.	damn, does this thing need an updated model
Ynnari Psyker	No official name, speciality necroman… I mean Spiritual and soul based powers. Yvraine, emissary of Ynnead
Avatars	The Yncarne, Avatar of Ynnead.

Dark Eldar

The Dark Eldar, however, are psychically atrophied compared to their Craftworld bros. They have to avoid using psychic powers due to Slaanesh's "I own your soul" gig, and Dark Eldar using psychic powers are reasonably feared as bait for snusnu-with-a-Daemonette. They can use psychic artifacts, like all those crazy living swords and Haemonculus toys; the only psychic power they use is their infamous emotion-vampirism ability that can replenish their bodies and souls. And kamehamehas, for Mandrakes. They do have extra fun torturing, killing and then weaponizing psykers though.

Tau Empire

The Tau race is incapable of producing psykers, due to having almost no presence in the Warp. The good news for them is that they don't have to worry about Bad Things, such as any members of their species spontaneously turning inside out from the anus and summoning an army of monsters that will fuck, kill, and eat people, (not strictly in that order). The bad news is that they have no way to develop psychically based technology, so their FTL travel is glacial, albeit a good deal safer than an actual Warp jump, and their FTL communications options are limited to the Space Pony Express. It should be noted that some of their vassal races have psychic abilities, including their own Navigator analogues. It is known that they actually locate, isolate and study human (and probably other species') psykers, but as the Immaterium is too irrational and far beyond their science they have had little success in analyzing the reason behind Gue'La suddenly going crazy and summoning teleporting armies of violent omnicidal "aliens" out of thin air.

• Funnily, the Kroot have psykers (they have a diverse diet) and understand a great deal about the Immaterium. They even have some crude warp vessels, usually with purchased or stolen xeno tech in it. How the Tau have gotten so far without bothering to ask their close allies about it all probably says something about the Tau's Greater Good and its inability to properly assimilate new cultures.

Necrons

The Necrons no longer have souls, so they have no presence in the Warp, and therefore can't manipulate it with their minds. And yet, they have managed to conquer the Warp with technology. (Egyptian Skeleton Zombie Robots, Yeah!) They keep fucking up the Warp and psykers with the gloom prisms they mount on their spiders, pylons (sounds familiar...), or even giant city-sized mechanisms that cut entire planets from the Warp. One in the Word Bearer novels even had...this thing, about the size of a resurrection orb, which blanketed an entire system in a "psychic black hole." Problem, daemons? There's also the Pariahs, a dangerous type of lychguard made from psychic blanks that act much like Culexus assassins.

Orks

The Orks are all passive psykers, or rather emanate their own gestalt "psykik" energy in the power of the WAAAGH!, though they're mostly unaware of this. A large number of Orks in one place will slightly alter reality to suit their wishes, turning jam-prone, dirty blunderbusses into fully-automatic rifles of rape. Weirdboyz are the only ones who can tap into it actively to manifest psychic powers, which have an amusing tendency to make Orks heads explode with absolutely no warning. As said above, the Orks draw psychic energy from each other, not from the Warp, which makes them virtually immune to Chaotic influences, although they do have a pretty serious presence in the Warp in the form of Gork and Mork (or maybe the other way round).

Ork psyker types in 40k:

Psyker type	Description	Image
Ork Wyrdboyz	Orks with Psychic powers, whats not to love

Tyranids

The Tyranids are innate psykers, and their collective power goes into the Hive Mind, which is what the big bugs tap into to manifest psychic powers rather than the Warp, the same way a Weirdboy would tap into the WAAAGH!. Only a few bugs are capable weaponizing the Hive Mind's psychic energy, the Zoanthrope being one such option for Tyranid psychic support. Few 'Nid species beyond the Zoanthrope are capable of firing tank piercing mind-lasers. Instead the other big bugs use its powers for buffs and a form of control called "synapse", which keeps the Tyranid horde from going feral and killing everyone and everything they see. If the Hive Mind gets driven away from the horde or the synapse bug gets killed, the synapse link collapses and the 'Nids turn feral. How Zoanthroapes still manage to retain psychic powers when they lose their link to the Hive Mind is not understood. Also, before Genestealers got retconned into being Tyranids, Genestealer Magi DID use the power of the Warp to power their abilities and could dedicate themselves to Chaos. There's an image of a Khorne Magus in one of the 2nd edition books...

Tyranids psyker types in 40k:

Psyker type	Description	Image
Zoanthrope	Scary floating Psychic bug monster
Swarmlord	Biggest scariest Psychic bug monster
Hive Tyrant	Big Scary Psychic bug monster
Broodlord	Another big Scary Psychic bug monster
Tervigon	A bigger scarier Psychic bug monster
Patriarch	A smaller but still scary Psychic bug monster
Magus	The most human looking scary Psychic bug monster

Squats

The Squats that grow very old are called "living ancestors". They are extremely rare, and develop psychic powers by communing with the spirits of their predecessors. And you could put them in an egg-shaped terminator armor, then onto a trike, with a bolt-firing cavalry lan-*BLAM* Squats are heresy!

Psychic Power Hierarchy

The Imperium of Man uses a 26-point scale (with gradations named for the letters of the Greek alphabet, for some reason) called The Assignment to determine the comparative psychic power of an individual. Unfortunately, this gets very confusing in the fluff, where Alpha-level psykers seem to be a dime-a-dozen and show up all over the place, and established characters that are canonically high on the scale are completely overshadowed by some other character. All of this "logically" leads neckbeards to reach the flawed conclusion that their favourite character on the tabletop MUST be Alpha level or greater.

Furthermore, it is canon that a psyker's place on the scale can change over time as his or her powers either increase with practice or decrease due to atrophy from lack of use. So generally, the fluff is quite useless for determining who is greater than whom; without the evidence of a direct psychic battle between any two comparing how they match up, it is pretty pointless to use this method.

Nevertheless, here is the scale, starting with the most powerful classification:

1. Alpha-Plus
   • Alpha-Plus psykers do not represent the top of the scale, but in fact are completely beyond the scale. These individuals operate on a completely different wavelength from normal people and are owners of completely alien mindsets. In terms of power, they are akin to weapons of mass destruction, flavored depending on their particular discipline; for instance, an Alpha-Plus Pyromancer is entirely different from (and significantly less dangerous than) an Alpha-Plus Telepath. However, in theory there is nothing that a trained Alpha-Plus psyker cannot accomplish through force of will, from snapping a Titan in half (Telekinesis) to summoning the Chaos Gods themselves (Malefic Daemonology). There is a tacit assumption that this category contains the Emperor and his "notably-psychic" Primarchs (especially Magnus the Red in his daemon Primarch form), but even he admitted there were limits on his power, specifically that one could not be both all-seeing and all-powerful at the same time. No attempt is made to distinguish power levels among members of this grade, even when they demonstrably differ in power (such as The Emperor and Magnus the Red).
   • Assumed Examples:
     • The Emperor
     • The Hive Mind
     • Other God-level and Demigod-level Psykers, such as Tzeentch and Magnus the Red, respectively.
     • Malcador the Sigillite is definitely up here as well, being the third-most powerful human Psyker (only outranked by The Big E himself and Magnus, a Demigod.
     • In terms of seventh-edition mastery levels, approximately 5+.
2. Alpha
   • It is very much assumed that the most powerful, mortal fluff characters, such as Eldrad Ulthran or Ahzek Ahriman, are Alpha-level psykers. There are a couple of Imperial Alpha-level psykers in the canon who still have their mental faculties and happen to be Grey Knights: Grandmaster Epimetheus, one of the original founders, and Prognosticar Hyperion.
   • Assumed Examples:
     • Ahzek Ahriman
     • Eldrad Ulthran (he is listed amongst the greatest of his race but there are other Eldar seers that rival him in power even if they are not named)
     • Grandmaster Epimetheus
     • Prognosticar Hyperion
     • Kairos Fateweaver
     • Inquisitor Lord Hector Rex, who bested An'ggrath IN CLOSE COMBAT
     • In terms of seventh-edition mastery levels, approximately 4.
3. Beta
   • Exceedingly rare and dangerous. The Imperium believes that human beings have not sufficiently evolved enough to contain Beta and Alpha levels of psionic talent without going completely bat-shit mental(Though exceptions do exist). Arvann Stern is Beta level. The Beta (or perhaps Gamma) level might also include the most powerful Chief Librarians of the Space Marines, like Varro Tigurius, Mephiston, and Ezekiel, and most of the more powerful Eldar Farseers. Very unlucky Alpha psykers may instead find Imperial service in the Ordo Sinister, meaning they'll get turned into screaming batteries for Psi-Titans.
   • Assumed Examples:
     • Arvann Stern
     • Be'lakor
     • Ezekiel
     • Mephiston
     • Varro Tigurius
     • Grand Master Voldus
     • The Swarmlord
     • The Yncarne
     • In terms of seventh-edition mastery levels, approximately 3.
4. Gamma
5. Delta
   • Approximately one out of every billion human births will produce a Delta- or Gamma-level psyker, who, for the Imperium, represent the "useful" upper limit of psychic potential without being too dangerous to let live, though it's up to the Inquisition to be the ultimate judge of that. The Inquisitor Gideon Ravenor was believed to be a high Delta-level psyker. The lower level Eldar Farseers might also be considered Delta- or Gamma-level, along with common Daemon Princes. The average chapter chief librarian will likely be around this level.
   • Assumed Examples (Gamma and Delta are folded together, as they are difficult to distinguish):
     • Castellan Crowe
     • Gideon Ravenor
     • Jensus Natorian
     • Grand Master Kaldor Draigo
     • Inquisitor Katarinya Greyfax
     • Inquisitor Torquemada Coteaz
     • Yvraine
     • In terms of seventh-edition mastery levels, approximately 2.
6. Epsilon
7. Zeta
   • Epsilons and Zetas represent your ranks of relatively strong psykers. The Primaris Psykers of the Imperial Guard, rank-and-file Space Marine Librarians and the lower level chief librarians will full amongst the upper range, garden-variety Chaos Sorcerers, and Eldar Spiritseers and Shadowseers could be counted among the Epsilon- and Zeta-levels, as well as Tyranid Hive Tyrants and Zoanthrope broods.
   • Assumed Examples (Epsilon and Zeta are folded together, as they are difficult to distinguish):
     • The Changeling
     • Ku'gath Plaguefather
     • Shadowseer Menahina Ylsa
     • The Spawn of Cryptus
     • In terms of seventh-edition mastery levels, approximately 1.
8. Eta
9. Theta
10. Iota
    • Iota represents the first "true" psykers who are able to manifest and control psychic abilities with a modicum of training. These are the people that find their way into the various Imperial institutions and become Sanctioned Psykers in Imperial armies. The average Eldar could probably be considered among the Iota to Theta levels, though most make minimal use of their inborn psychic potential except for maybe an occasional telepathic communication. The Eldar who train as Warlocks might reach the Eta level. Ork Weirdboyz, who represent the highest extent of psychic potential in individual Orks, have reached about Iota, though this has the potential to be massively boosted by a sufficient amount of WAAAGH! energy, provided they can keep their own heads from detonating.
    • Assumed Examples (Eta, Theta, and Iota are folded together, as they are difficult to distinguish):
      • There are no named characters known or strongly suspected to be at this level, although smart money would be on the named Ork psykers, like Old Zogwort or Big Redd.
      • In terms of seventh-edition mastery levels, approximately 0 (this is the appropriate grade for members of a Psyker Brotherhood who are only substantively powerful in aggregate, like Wyrdvane Psykers).
11. Kappa
12. Lambda
13. Mu
14. Nu
15. Xi
16. Omicron
    • You get a broad range of people who can manifest psychic talents either unconsciously or so subtly as to be beneath the notice of everyone but the Inquisition, such as performing minor "magic" tricks or divinations. Most of the time they are quite useless but still represent a danger since they can be possessed. An Omicron might be able merely to predict consistently what someone will do right before they do it, while a Kappa might be able to move objects by concentrating or create flames out of thin air. These individuals may use their abilities to become petty crime lords, expensive hitmen, or fortune tellers. Although the Inquisition is too busy to sort out everyone at this level, the Imperial public is conditioned well enough to spot and ostracize these witches if the truth about them ever comes to light in their societies. (Read Gaunt's Ghosts.) An ordinary Ork would likely register somewhere in this area—that is, psychic enough to contribute to the gestalt field that Orks will produce in great enough numbers, but not psychic (or smart) enough to actually harness that power and bend it to his will. The same is true of basic Tyranid species, who are psychically linked by the Hive Mind, but not psykers individually.
17. Pi
18. Rho
    • Run-of-the-mill humans, neither psy-active nor psy-inert. A generally safe place to be. If this scale was a number line, Pi and Rho would be zero.
19. Sigma
20. Tau
    • When you start descending below the scale of humans, into the "negative" side of the scale, you start going psy-inert. When psychic effects start manifesting subtle phenomena that most people would describe as something feeling "off", people at the Sigma/Tau level can't tell anything is happening. Amusingly enough, this level contains the Tau race, who have no psykers and (little to) no signature in the Warp. The Necrons, machines who long ago sold their souls to the C'tan, could also be found in this level.
21. Upsilon
22. Phi
23. Chi
24. Psi
    • These are individuals with varying degrees of immunity to psychic powers. They are not true Blanks (see below), but they may reduce an incoming power from something absolutely lethal to something survivable, or are much more difficult to mind-read than most people. The appropriate grade for most Sisters of Battle or other devout members of the Ecclesiarchy.
    • Assumed Examples:
      • Saint Celestine
      • Uriah Jacobus
      • In terms of seventh-edition mastery levels, approximately having the rule Adamantium Will without having the Psyker rule.
25. Omega
    • Usually referred to as Untouchables, Pariahs, or Blanks. Not only are they immune to psychic powers, but they can also inhibit the powers of psykers around them and/or neutralize psychic effects on an area around them. The Imperium trains its human Blanks as deadly Culexus Assassins, who are professional psyker-hunters, as it did the Sisters of Silence before them. The Eldar, believe it or not, also produce the occasional Blank, and these become the infamous Solitaires of the Harlequins.
    • The fluff is a bit inconsistent on the exact limit of a Blank's ability, but that's fine, because in Dark Heresy, Blanks exhibit a broad range of effects which can be different from person to person, much like high-level psykers can have different powers and disciplines. True Blanks have such a psy-negative effect that even normal people can sense it, and it manifests as an irrational loathing for the Blank, though in some cases it can be offset by either a good personality (Alizebeth Bequin) or an odd character trait (Gunner Jurgen). For psykers, however, Omega-level persons are physically and mentally painful to be near. After some training, Blanks can actually benefit from the psychic power they suck from their surroundings (having psykers or even normal living beings in those surroundings really helps), which they use to empower and invigorate themselves. Culexus Assassins take this even further with their Animus Speculum helm by shooting mind-bullets formed from that energy.

There have, however, been a few occasions where a Blank's abilities have been overwhelmed or even permanently shutdown. Bequin's blankness was overwhelmed by the warp corrupted psi-sentience of a Chaos Titan and Wystan Frauka's Blankness was gradually eroded away over time till he was able to be possessed by a psyker.

1. • Assumed Examples:
     • Alizebeth Bequin
     • Gunner Jurgen
     • In terms of seventh-edition mastery levels, approximately -4.
2. Omega-Minus
   • The Yin to Alpha-Plus's Yang, Omega-Minuses, or Black Pariahs, are so extremely rare that it's a safe bet only one of them (an assassin named Spear) ever existed in our galaxy at any point in time. Their null-aura is so powerful that it drives even normal humans insane (and eventually kills them, unless they kill themselves first), and psykers and psychic artifacts within their aura simply cease to exist, turning into dust in a matter seconds. Even other Pariahs are terrified of them. Basically, anybody with the classification Omega-Minus is a Warp black hole that only exists to suck in all souls and Chaos energies and turn it into void. That means the people who get killed by these fucking terrifying abominations have their souls sucked out and completely destroyed. It's not as terrifying as it sounds, though, as being utterly destroyed upon death certainly beats being raped by daemons for all eternity.

   The only known example of a Black Pariah was bonded to a minor daemon by Erebus, so their aura does not appear to eradicate daemons. On the other hand Spear's clone-fetus made by the Inquisition and placed in an anti-warp projection device known as "the Black Lantern" had shown the ability to liquefy high-level psykers and perma-kill greater daemons all the while creeping the hell out of the regular humans, although it could be attributed to the device focusing and amplifying the Black Pariah aura not unlike the Animus Speculum does with regular Blank auras.

   • Assumed Examples:
     • Spear (Assassin)
     • In terms of seventh-edition mastery levels, approximately -5.

Other Factors

When you get further into the details, not only is sheer psychic potential a factor to consider in determining how powerful a psyker is, there are other things to consider when trying to figure out mechanically how one differs from another.

This is easier to do outside of the tabletop setting, which focusses on a d6 scale, where a minor difference in a single statistic can create one power tier an order of magnitude more effective above another.

Level of Control

The Willpower (read: control) of a given individual holds almost about as much sway in saying who is more powerful than who, so just because a psyker has an mid-high psy rating, if their Willpower is low (say: 30) they're less likely to successfully manifest but are more likely to create a powerful effect when they do. Inversely, a low-mid rated psyker with a strong willpower (say: 60) is more likely to successfully manifest and is also more likely to be able to resist/counter incoming psychic effects.

That said, even in the mechanics of the RPG rules, once a psy-rating reaches epic heights then they should have no problems casting even with a low willpower.

Sorcery

The second thing to consider is the whims of the Chaos Gods, (particularly Tzeentch). Sorcery is entirely separate from Psy Rating/Assignment and even a non-psyker with the correct rites and incantations can pull off similar (if not the same) manifestations as a true psyker. Back during the Horus Heresy, Erebus (and 30k Word Bearers with Burning Lore) is an example of this.

A true psyker with access to sorcery can increase his power levels even higher and can easily outstrip more powerful psykers than himself, though Sorcery comes with its own perils and generally leads to Damnation and Corruption (no wonder big Emps put his foot down at the council of Nikaea)

Furthermore, certain favours gifted from the Gods also increase psychic output. It used to be that in days gone by, the Mark of Tzeentch used to enhance psychic potential on the tabletop. Nowadays it doesn't, but in the RPG it still does. But obviously once you've been marked by a God of Chaos, you're in their pocket forever, and you best do your utmost to keep them happy or you end up becoming that-which-shall-not-be-named.

Pushing

Separate from either issue is the fact that Psykers can theoretically increase their assignment rating for a brief instant in order to grant themselves more power.

In both the rules and the fluff there are common instances of psykers being able to boost themselves and create larger effects or to overcome more powerful opponents. This is not so prevalent on the 40k tabletops (although with the 7th Edition advent of the shared Warp Charge "Pool" this may be untrue) and not all psykers have the ability to do this to the same degree.

One method is to "Push" their powers further, basically taking a gamble and temporarily adding MOAR power to their manifestation.

• Bound psykers (that is to say, nearly every Imperial psyker who has undergone a Sanctioning process [Including Librarians] or Soul-Binding) can only push themselves so much and they are at greater risk of something bad happening (ie: Perils of the Warp) when they do so.
• Unbound psykers (Rogue Psykers / Sorcerers) on the other hand can reach even higher degrees of power but shit WILL hit the fan.
• Daemonic psykers who attempt to push their powers can go yet higher, but are considerably more likely to cause dangerous psychic phenomena. However since their mere existence on the material plane can be considered a dangerous psychic phenomena they are less likely to be bothered by it unless it is a straight up Perils of the Warp.

Psychic Disciplines

There are five "basic" psychic disciplines in the grim darkness of the future. Generally speaking psykers prefer to focus on one discipline if they seek more power, but doing so runs the risk of changing their mindset, as connection between psyker's mind and the Warp is two way, and if one is to use his mind to alter the Warp, warp would use that connection to alter psyker's mind. Some psykers fight this, some don't, and most don't live long enough for this to take effect.

• Biomancy is about flesh/life force manipulation and shooting lightning, somehow (probably bioelectricity, but depending on your interpretation, either pyromancy or telekinesis fits this power better). Old and powerful biomancers tend to become quite sick fucks, building cruel and sadistic tendencies over time.
• Divination is about predicting and tweaking the future. Old and powerful diviners are known to be extremely nerdy, hoarding massive amounts of knowledge about deciphering visions and omens and general theory of the Warp, but this often comes at the price of constant melancholia and depression, as they realize how much of a puppets in the hand of Fate they are. Unless that diviner is Ahriman, who decided to skullfuck Fate and be the one in charge of his own destiny (though even he went though an "I'm just a puppet" emo-phase before it).
• Pyromancy is about conjuring and throwing fire at people. It comes to no surprise to anyone that pyromancers that happen to live long enough without blowing themselves up often to grow into aggressive pyromaniac hotheads that tend to solve all problems by KILLING IT WITH FIRE.
• Telepathy is pretty much self-explanatory - reading and translating minds. Mind control and mind rape goes there, as well as invisibility, even though this power renders you invisible to things without minds. In terms of long-term personality changes Telepaths draw the absolutely shortest straw, as over time they "pick up" bits and pieces of personalities of people they mindraped, risking to lose their original selves eventually, and even if they have the will to resist it, they inevitably grow into absolute misanthropes due to knowing too well what disgusting things people around them think about all the time.
• Telekinesis is also obvious - moving things with a mind. Here also goes psychic shields and somehow dimensional gates. Not much known about how it affects psyker's psyche - old telekines are known to being quite stoic, even stubborn but many unspecialized psykers that manged to survive for long without losing their minds also tend move towards this archetype, so it's debatable whether it's discipline effect or a simple natural selection.
• Daemonology is a sixth common discipline, although it's by no means basic, being much more difficult to learn and dangerous to use (as anything that directly deals with chaos daemons carries the possibility of the psyker's head exploding into a warp portal). It's split into two sub-disciplines - Malefic is about summoning daemons and using their power, and Sanctic is about banishing them and killing things with the refined unshaped Warp energy. Generally speaking most dedicated daemonologists do not live long enough to experience any personality-changing effects of their discipline, and those that do are either brainwashed on a regular basis (Grey Knights) or are already Chaos-corrupted and affected by daemonic pacts (Chaos sorcerers and wild psykers).

Besides those six, other disciplines exist, although they are mostly faction-specific:

• Chaos psykers and daemons use their own specific disciplines, dedicated to one of the three gods who don't hate sorcery:
  • Tzeentch is mostly about mutation, subjugation, and manipulation of the warp itself. Tzeentchian powers typically revolve around controlling the energies of the warp itself to damage foes (like Doombolts), mind-reading and controlling people, and manipulating reality to either open warp rifts or mutate their opponents into those-which-shall-not-be-named.
  • Nurgle is like a twisted version of Biomancy, focusing on the psyker spreading the gifts of Papa Nurgle by polluting their surrounding area with his many plagues and contagions, causing most people to succumb and die within minutes. The "beneficial" parts of these are mostly related to raising a recipient's endurance, as the many blessings of Nurgle can do anything from mending grievous wounds in an instant, to granting them inhuman resistance to damage.
  • Slaanesh tends to be the trickiest, focusing on illusions, and manipulating their targets' senses to either control them or drive them into the throes of insanity (Which can either be good or bad depending on the power involved). Slaaneshi powers are a bit similar to Tzeentchian ones, although are focused more around manipulating the physical and mental characteristics of people to the extreme (something they have control over), rather than their fates and surrounding reality (which people typically do not).
• The Eldar have developed four disciplines of their own; the first two use runes as proxies to manifest psychic powers, so they don't get mind fucked by Slaaneshi daemons the moment they surge in the warp for the power, and they created two disciplines to utilize those runes:
  • Runes of Fate Used by Farseers is kind of like Telepathy and Divination mixed together and shaken a bit - same kind of future telling and mindrape in a slightly different form. Except for Eldritch Storm, which looks like it was pulled form the Sanctic Daemonology
  • Runes of Battle Used by Warlocks and Spiritseers. Features a set of powers that can be used to buff allies or debuff opponents, most of which don't fit into any of the basic disciplines.
  • Harlequin Shadowseers also use their own discipline called Phantasmancy, which is basically Telepathy on an acid trip, as the psyker channels his own killer-clown kind of batshit insanity into people, and polishes it out with hallucinogen grenades thrown on the top.
  • Eldar Corsairs, being cool space pirates, do not utilize rune stones, and channel psychic powers the old way, at a higher risk of being raped by daemons. Their old-school techniques allow them to use pre-fall magic called Aetheromancy, designed to utilize the Webway (similarly to how Sanctic Daemonologists utilize the Warp), so they can project a guidance map, teleport their allies through it, and create rifts that suck their enemies into it.
  • The new Ynnari faction brings with it the new Revenant discipline which looks suspiciously like Necromancy but isn't we swear.
• Ork Weirdboyz have their own discipline, that runs on Waaagh! energy rather than the Warp, and don't have access to other disciplines. Surprisingly, Waaagh! powers are quite powerful and some of them are tricky, although they are mostly focused on pumping the boyz around the Weirdboy with buffs, getting them closer to enemies or killing shit with green lightning.
• Similarily, Tyranids, whose psychic powers also run on a collective psychic field, have a specific discipline, which is Telepathy with a bit of Biomancy and the odd Zoanthrope mind bullet power thrown in.
• Spaсe Marine librarians have developed not one but FOUR special disciplines, which Chaos Sorcerers rename because they have to be different:

• Technomancy/Heretech Telepathy/biomancy for machine spirits rather than living beings, for those who prefer the company of machines or like to wreck enemy ones.
• Fulmination/Ectomancy Biomancy that throws away all that life force and biochemistry shit and focuses solely on the lightning. All the lightning!
• Geokinesis/Geomortis If you ever wanted to be an earthbender this is the discipline for you. Among other things it allows you to move buildings, hills and forests around.
• Librarius/Sinistrum Very Eldar-runes-like telepathy/divination based discipline with trickery thrown in.

• Space Wolf Rune Priests use a discipline called Tempestus (although they refuse to admit it's a psychic discipline at all, since they're hypocrite assholes) - it involves powers that mostly revolve around ice, earth, and storms. It looks like it utilizes a psychic ice effect, which is a common side effect of manifesting powerful non-pyromancy powers, and then they mix that with a bit of Telekinesis to spin that ice around or shape it into giant killer wolves that eat you alive.
• Blood Angels and their successors claim to have their own discipline called Sanguine but it's really just a bunch of Biomancy, Telekinesiss and Telepathy powers thrown together and given fancy names. Their buffing spells have a tendency to affect allies, rather than just the psykers at the cost of sheer power, possibly due to the selfless nature of their chapter. Then there's the Blood Lance - which is just the entirety of their psychosis bottled into one power, with all the heat and fury of the Black Rage with the color of the Red Thirst.
• The Dark Angels utilize the Interromancy discipline, which is a specialized variant of the Telepathy discipline, originally designed to interrogate Fallen FOUL TRAITORS WHO ARE NOT IN ANY WAY CONNECTED TO THE FIRST LEGION. It may lack some of the most bullshit OP powers of true Telepathy, but has a strong combination of buffs and debuffs and the latter have a chance to permanently cripple their targets, especially if they are weak-willed.

Comparing Psykers

Addendum: This list is subjective in the extreme. Trying to compare the Psychic powers of so many characters without a standard metric is fukkin' stupid.

1. God-Emperor of Mankind, The Hive Mind, Chaos Gods and other Deities.
2. Magnus the Red
3. Eldrad; Malcador the Sigilite; Lorgar; Azhek Ahriman.
4. Epimetheus; Warlock Titans.
5. Eldar Farseers; other Alpha level psykers; Lords of Change.
6. Rubric Sorcerers; Tigurius; Sevrin Loth; Mephiston; Njal Stormcaller; Ezekiel; Kaldor Draigo.
7. Chaos Sorcerers; Grey Knight Librarians; Ravenor; Hyperion; Swarmlord; Zaraphiston; Shadowseers (Harlequins); Spiritseers; Worldsingers (Exodites); Wraithseers (power equal to the seer used in its construction).
8. Regular Librarians, Zoanthropes; Eldar Warlocks; Bonesingers; Corsair void dreamers (tend to be random in power with some being the equal of Farseers).
9. Primaris Psykers; Hive Tyrants;
10. Wyrdvane/Sanctioned Psykers; Ork Wyrdboyz; Zoanthropes;
11. Regular Grey Knights; Navigators; Astropaths (they are powerful, but their powers are normally so specialized at being a cell-phone, most of them are no match for 'true' psykers).
12. Regular Eldar.
13. Regular Orks.
14. Regular Humans.
15. Blunted Humans; Tau; Regular Space Wolves.
16. Necrons.
17. Blanks/Pariahs.
18. Culexus Assassins/Sisters of Silence - farthest from Psyker as possible, soulless anti-psykers.
19. The Black Pariah (Daemon-Blanks?)

I'm not sure about the place of Greater Daemons here; also, Tyranid psykers.

Gallery

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  You should never invite psykers to your poker night.

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  Culexus assassins are psykers' worst nightmare, though they are very friendly.

• Psyker Dredd knows you were gonna say that.

  Psyker Dredd knows you were gonna say that.

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  Shh, my heresy sense is tingling...

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  The Adeptus Astra Telepathica's easy steps in identifying and capturing potential psykers.