- "I can pulp your flesh and snap your bones in less than a second and without so much as lifting a finger. What is the power of technology compared to that?"
- — Vel'Cona, Chief Librarian of the Salamanders
Librarians are the psykers of the Space Marines who survive an Adeptus Astartes Chapter's rigorous screening and training to bend the powers of the Warp to their will for the benefit of their fellow Battle-Brothers and in service to the Emperor of Mankind. Beyond their psychic duties, the Librarians of the Astartes are also expected to record the great deeds of their Chapter and maintain the Chapter's storehouse of ancient lore, the functions for which they are named. A Librarian is often estranged from the other members of his Chapter. This is usually because the psychic abilities he possesses are what his brother Space Marines are often expected to abhor and purge in most other beings. Space Marine Librarians use their abilities to serve the various undertakings of their Chapter; however, their actual place in the order of battle is always with the Librarium in a Codex Astartes-compliant Chapter. As the name suggests, the Librarium is a place within a Space Marine Chapter's fortress-monastery where the Chapter's vast knowledge base, gathered over millennia of hard-fought battles and participation in engagements the length and breadth of the galaxy, is stored.
Space Marine Librarians are generally classified in one of four ranks, each with its own duties and responsibilities within the Librarium. The Librarium is led by the veteran Space Marine psyker who bears the rank of Chief Librarian. The Chief Librarian is usually, but not always, the most venerable of his psyker brothers. The Chapter's most potent battlefield psykers are the Epistolaries, each a hardened veteran of many wars. The Chapter's psychic communications and the Librarium's records are maintained by the Codiciers and the Lexicani (sing. Lexicanium), respectively. These ranks and responsibilities may vary from Chapter to Chapter.
The Imperium is eternally vigilant for the taint of mutation. Space Marine Chapters are, if anything, even more careful to ensure that their gene-seed is not polluted. Apothecaries rigorously screen potential recruits for any sign of genetic deviation, but not all mutation is physical. Psychic talent is a mutation too, and is at once the most dangerous and the most useful. The training of a Chapter's nascent psykers is one of the many responsibilities of the Librarius.
Few normal Space Marine recruits survive the rigorous training, enhancement and indoctrination required to join a Chapter. Amongst Librarians, the attrition is far worse. The Aspirant must not only endure everything a normal recruit would, but also have a strong enough spirit to withstand the moulding of his mind. A recruit must be taught how to hone and wield his powers, and how to protect himself from the Empyrean's innate hazards. A Librarian faces a thousand enemies before he even goes to war –- to the creatures of the Warp, his mind is a choice prize. Each day is a walk along a precipice, and a false step can see him tumble into madness.
If a recruit survives the rigorous testing, he joins the Librarius as a Lexicanium, rising through the ranks to become Codicier, Epistolary or perhaps even the Chapter's Chief Librarian. He will use his abilities to pierce the Warp and provide the means for interstellar communication, as well as to identify others of his own kind. He will judge them as he was himself once judged, scrutinising potential candidates and peers for frailty of mind or spirit. A moment's weakness can unleash untold evils, and vigil must be kept against any wavering of purpose.
In addition to training psychic recruits, the Chapter's Librarius is also charged with recording the history of the Chapter. Librarians hold a functionary rank, describing their role within the Librarius as well as their position within the Chapter's hierarchy. Lexicaniums, for example, are responsible for preparing reports of battle for the Chapter's records, whilst Codiciers provide a strategic overview of the whole theatre of a war. After decades of study and book keeping, a Librarian will be well-versed in the history and lore of his Chapter, and both his wisdom and counsel will be highly regarded by the Masters of the Chapter.
Most Librarian battle-disciplines focus on enhancing their already formidable combat prowess. Many can use their psychic powers to throw powerful energy bolts, project force shields or increase their might to demigod-like proportions. Some can step outside of time, slow the enemy's movements or redirect bullets with the sheer power of their minds. Even so, the most skilled Librarians can master more subtle gifts, learning how to read the Emperor’s Tarot and sense the movement of daemons through Warpspace. A Librarian can feel the psychic shock waves that herald the arrival of a voidcraft from the Warp, or the turmoil they leave in their wake as they depart realspace. These powers, and more, set Librarians apart from their Battle-Brothers, yet their presence is always welcomed on the field of battle. In all of the Imperium, there are few greater warrior mystics than Space Marine Librarians, with their potent combination of the prowess of an Adeptus Astartes with the unearthly powers of the Warp.
The Imperial records concerning the origins of the Space Marine Librarians are murky and mired in legend rather than hard facts like much of the history of the Imperium's early days. However, according to the chronicler Saphrus the Ancient, during the Great Crusade of the early 31st Millennium the Emperor of Mankind held a great Imperial conclave, the Council of Nikaea, on the newly-terraformed planet of the same name, to determine whether human psychic powers and the practice of psychic sorcery presented a danger to the newborn Imperium of Man and its people. Within the Imperium there were those, like the Thousand Sons Space Marines Legion of the Primarch Magnus the Red, himself a powerful psyker, who had an extremely high rate of psychic mutation and regularly used psychic abilities and sorcery to expand the growing Imperium's reach across the galaxy. Others, such as the Space Wolves Legion of the Primarch Leman Russ and the Witch Hunters known as the Sisters of Silence, held that all psykers, even those who were Astartes like the Thousand Sons, represented a grave threat to the human race. Some Primarchs had accepted the ideas of Magnus on the beneficial use of psychic abilities in their own Legions, while others like Leman Russ refused to deal with what they saw as dishonourable deception and unnatural witchery and outlawed all psychic powers as simply sorcery by another name.
The Emperor invited the advocates of both sides to attend the conclave and at the Council on Nikaea they argued each other to a standstill. It was only the intervention of a contingent of Space Marine Librarians from the other Legions besides the Thousand Sons that presented a compromise. Their proposal was that while the Imperial education of psykers to best serve humanity should be made a priority, the conduct of psychic sorcery would be outlawed as an unforgivable heresy, since psykers were simply tools who could serve Mankind for good or ill, but the powers of sorcery could only be gained by treating with the foul denizens of the Warp whose malevolent intentions were often manifest. This compromise was rejected by the Emperor once it was revealed that Magnus the Red had continued to explore the power of sorcery after the Emperor had warned him of its dangers. The Emperor disregarded the proposed compromise and ordered all of the Space Marine Legions to disband their Librariums and for Astartes Librarians to return to service as line warriors and never use their psychic abilities again. Unfortunately, after the outbreak of the Horus Heresy, it became clear that the Forces of Chaos could not be defeated unless the Loyalists were also able to draw upon the power of the Warp. Following the end of the Heresy, the original compromise proposed at Nikaea was adopted as law without a provision for rebuttal, and it has stood for ten thousand standard years as the official policy of the Imperium on the use of psychic powers. Today, in the 41st Millennium, each Chapter remains vigilant to ensure that new recruits will not taint the gene-seed of the Chapter through mutation. However, the psyker mutation is often encouraged, and these Astartes are then inducted into the Chapter's corps of Librarians.
At the centre of a Chapter’s fortress-monastery there usually lies a vast sealed chamber known as the Librarium that is filled from floor to ceiling with books, scrolls, and data crystals. Overseen by the Chief Librarian and maintained by Lexicaniums and Codiciers (supported by a small army of Servitors and Chapter Serf scribes who work ceaselessly), the Librarium is the repository of all the Chapter’s knowledge and history. Even within the Chapter, few are given access to this chamber and fewer still have the chance to study its texts. Even the most well-read Imperial scholar or Administratum Adept can only guess at the secrets and lore contained within one of the fabled Space Marine Librariums. This repository is a wealth of knowledge that the Chapter Master guards well, knowing that in times of need he may have to call upon the counsel of his Librarians and the lore they possess to guide him in battle.
In the heart of the Librarium there is also a smaller inner chamber, carefully sealed and protected, known as the Librarius. This is where the Chapter stores its artefacts, trophies, and proscribed texts, many of which are taken from the corpses of Heretics and aliens—unfit or too dangerous for the eyes of any but the Chief Librarian. It is often a point of friction between the Ecclesiarchy and the Adeptus Astartes that its Chapters possess such items or take them from their foes in battle. Of course, not even the most reckless Imperial Cardinal would dare consider confronting any Space Marine Chapter over this matter.
- "The power of a psyker is darkness, fire, and death, given life and purpose to rend souls and break minds."
- — First line of the Litany of Lies and Truths
Psychic powers are the physical manifestation of a Librarian’s abilities, and mark him as distinct from any other individual within a Space Marine Chapter. Librarians of Codicier rank and above make use of their psychic abilities in combat. These include the ability to project their consciousness above the battlefield so that they can get a bird's-eye view of the combat in a ritual that commences with the recitation of the Litany of Sight Beyond Sight. Doing so opens a wound on their forehead exposing their psychic Third Eye, which allows them to view locations that would normally be obscured. Librarians can channel psychic energy (often through Force Weapons) to deal greater damage than a normal melee attack would allow. They can also read the minds of others, unless they are protected by psychic shields. Some Librarians are sensitive enough to determine the last thoughts of the dead before their souls were absorbed into the Immaterium and can even see the emotions that have strongly influenced a place. Librarians are capable of telepathic communication across vast distances and can also read the ever-shifting tides of the Warp, allowing them to sometimes demonstrate the capability of foreseeing probable futures through limited displays of precognition. Other psychic combat abilities commonly used by Librarians include the following powers:
- Astrotelepathy - Librarians can use their gifts to send psychic messages and communications across the vastness of the void in the same manner as an Astropath. It is, however, a task that is undertaken sparingly, as like much of the rest of the Imperium’s forces Space Marines make extensive use of Astropaths, reserving their gifted Battle-Brothers for more vital tasks. Any Librarian can use Astrotelepathy, provided he has enough time and skill—yet sending a message across the stars is a far cry from communicating with someone on the same world or even a vessel in orbit.
- Compel - This power allows the Librarian to force others to briefly act against their will.
- Dominate - The Librarian may take over the mind of another, controlling his victim with his will.
- Inspire - A Librarian can bolster his Battle-Brothers by sending out waves of reassurance and calm.
- Long-Range Telepathy - This ability functions just the same as Short-range Telepathy, but with an extended range. In addition, once the psyker learns this power, such is his mastery of telepathy that he no longer incurs a chance of invoking an unwanted psychic attack or other phenomenon from the unpredictable eddies of the Warp when using either Short- or Long-range Telepathy.
- Mind Probe - This power allows the Librarian to peel back the layers of another’s mind to read the basic surface thoughts and then penetrate beyond.
- Mind Scan - A Librarian can extend his mind to contact and identify other sentient minds within range, even if they are out of sight, enabling him to garner impressions and information about the consciousnesses.
- Short-Range Telepathy - A Librarian can send his thoughts into the minds of those around him for a short distance, making a generalised broadcast to every mind within a short range indiscriminately.
- Augury - By reading the Emperor's Tarot for a specific individual, the Librarian can grant insight into what troubles lie ahead. During the reading both the Librarian and the subject must remain in physical contact and no other actions may be taken by either of them. The psyker must then ask a specific question. After making their specific inquiry, the Librarian is able to read the Emperor’s Tarot for the subject as they both concentrate on the question asked. At the end of this time the psyker interprets the Tarot and garners the results. The Warp is a capricious thing and seldom gives straight answers, often wrapping truths in riddles and lies.
- Divination - The Librarian can use this power to locate and track down a single object or person in his immediate vicinity. He can find anything, but there must be some degree of familiarity such as touching an object. When seeking an individual, the Librarian must have seen the person he wants to find, or the subject’s true name.
- Lifting the Veil - Lifting the Veil is an extension of the art of Psychometry and allows a Librarian to look beyond individual psychic traces and relive the past of a place or item.
- Possibility Shield - Using his understanding of future events and his perception of the flow of time, the Librarian is able to surround himself and nearby allies in a possibility shield which makes certain events more likely and others, such as being injured or slain, less so.
- Psychometry - Learning to read the Emperor’s Tarot is in part the act of learning to divine the Emperor’s word from psychic impressions. Refining this skill allows the Librarian to learn more about others from the crude psychic traces they leave behind on objects in the world around them. In this form, the Librarian can gain rough impressions from a personal object such as an article of clothing or a weapon. The level of information he gains depends upon how potent his individual psychic abilities are.
- Reading - Librarians that have the abilities of Diviners can read a person’s aura, the unconscious projection of his soul into the Warp. This is a very pale shadow, unnoticed by most beings, but a diviner can study this aura to learn about the person. When the Librarian activates divination, he can attempt to read the aura of any person he can see.
Codex Astartes Powers
- Avenger - The Librarian summons up the ancestors of his Chapter and shapes them into a flaming, vengeful avatar of death. The construct then billows forward to incinerate those in its path.
- Force Dome - Summoning up a shimmering field of force, the Librarian fashions a shell around himself and nearby allies. The shell is a sphere extending up to the radius around, above, and below the Librarian and protecting him and any within it. This shell provides protection against all kinds of ranged attacks or hazardous environmental effects, even trapping air and water within it. However, it will not stop melee attacks or creatures (friend or foe) that may pass through it without restriction.
- The Gaze of Infinity - Rending the veil between worlds, the Librarian creates a rift through which he and his allies might pass. The size of the rift depends on the power used to create it. The rift will remain open for a short amount of time or until the Librarian himself passes through it, at which time it will instantly close. This power is incredibly taxing and requires at least 12 hours of recovery time before it may be used again.
- Iron Arm - The Librarian sheathes his arm in an impenetrable field of energy with the power to ward off powerful melee attacks. Unfortunately, this power prevents the Librarian from using his arm for any other purpose, such as wielding a weapon, climbing, and so on.
- Machine Curse - The Librarian calls down a terrible curse on nearby machines and vehicles. The Librarian can either target a single vehicle (such as a battle tank or Land Speeder) or a number of mechanical devices (such as guns or Servitors).
- Might of the Ancients - Tapping into the deadly powers of the Immaterium, the Librarian infuses himself with psychic energy, increasing his psychical prowess and strength of arms to exceptional levels, to vanquish the foes of the Emperor of Mankind. This ability is most useful to the Librarian when used during melee combat.
- Smite - The Librarian conjurers up lethal bolts of lightning that leap from his hands to burn and blast his enemies into ash.
- Veil of Time - The Librarian attempts to predict the near future, seeing the flow of events and the actions of others. While this power is in effect, the Librarian benefits from this foreknowledge.
- Vortex of Doom - In a moment of pure desperation, the Librarian unleashes the full force of his psychic talents. With an utter disregard for reality, the Librarian opens up a flickering vortex in the fabric of space-time. The vortex is 2 metres in diameter and may be placed anywhere within range of the psyker. Once created, however, the Librarian has no more control over it. Having an open rift to the Warp is dangerous to the souls of anyone present. The Librarian making use of it can easily lose control of the Warp vortex the first time any creature comes within 10 metres of it, unwittingly unleashing it on friend and enemy alike until it has run its devastating course.
The Aspirants and newly-implanted Neophytes of all Space Marine Chapters are screened by the Chapter's Librarians for signs of psychic capability. Those who possess the potential to become a Librarian are then forced to undergo the same trials and sufferings all other Space Marine Neophytes of their Chapter face, but they also have to learn to harness their powers and protect their minds from the daemonic dangers of the Warp. As Space Marines are far stronger mentally and physically than an ordinary man, their flesh is ideal for daemons to inhabit as a daemonhost. For a Librarian, each day is a long walk along a narrow path which, should they stumble or stray, leads only to madness, possession and the deaths or destruction of all that they hold dear. The training within a Chapter to become a Librarian is very difficult, as new Librarians must not only be strong enough to survive the rigours of their training, but possess enough mental discipline to fend off the daemons and entities of the Warp, as these creatures see the enhanced form and mind of a Librarian as a great prize through which they could work much evil in the material world.
Each Chapter selects its Librarians in its own way, either from seed worlds, as it does with the bulk of its Initiates, or from the ranks of gifted psykers brought to the Scholastica Psykana. Most Chapters train and test chosen psykers following the ancient ways laid out in the Codex Astartes. Librarians of the Ultramarines, Blood Angels, Dark Angels, and Storm Wardens are all trained in this way, and, with few minor traditional variances, have been taught to live by the word of the Codex. There are, however, a few notable Chapters that do not follow the Codex Astartes and its laws regarding the treatment and control of psykers, including:
- Black Templars - Deeply religious and reverent of the Emperor, the Black Templars are zealots with a deep and abiding hatred of the witch. Such is their disdain of those with psychic powers that they count no Librarians amongst their number lest they foul the Chapter’s pristine gene-seed. The tasks of the Librarian, such as record-keeping and the study of lore, are divided among scholarly Battle-Brothers without the taint of the witch within the Chapter. Often an individual Black Templars Space Marine or Chapter Master will be responsible for maintaining a record of his own deeds—inscribing them on his armour so that nobody may doubt his courage or lineage.
- Space Wolves - There are few things that are "standard" about the Sons of Leman Russ, and so it is no surprise that they treat their psykers differently than the rest of the Adeptus Astartes. The Space Wolves do not have Librarians or even a Librarium, scorning such dusty and lifeless collections of knowledge. Instead they adhere to the ancient Fenrisian traditions of their ancestors, and those with psychic gifts become Rune Priests—skalds and storytellers who keep the Chapter’s practices and history alive through millennia-old oral traditions. While Rune Priests use their own powers and train in their own way, they function much as other Space Marine Librarians do, tapping into the Warp and drawing forth power to create psychic effects and reshape reality.
- White Scars - The Zadyin Arga or "Stormseers" of the White Scars perform the same functions as other Chapters' cadre of Librarians, though the Stormseers emerge from the deeply-ingrained mystical traditions of the tribal shamans and holy men who rode the plains of Chogoris with their Primarch Jaghatai Khan before the coming of the Emperor to Mundus Planus. Since the time before their Chapter's inception, when they were the shamans who first named Jaghatai Khan the Great Khan of the nomadic tribes, the Storm Seers have been called upon to continue to induct Neophytes and newly elevated Khans of their Chapter. The other responsibilities of the Storm Seer include teaching Aspirants the core beliefs of their Chapter. They firmly believe it is the manifest duty of the White Scars to destroy the enemies of the Imperium, awaiting the day that that Emperor will rise again, signaling the return of their lost Primarch and the beginning of the next Great Crusade to unify all of humanity. The Storm Seers believe that their powers are connected to the animistic spirits of the land and the air, and that as long as these natural forces fight alongside them, the White Scars will always be victorious. These elemental, animistic beliefs and the highly stylized Force Staff used by Storm Seers tie these warrior-mystics to their shamanistic past on the steppes of Mundus Planus.
- Grey Knights - All Grey Knights possess a degree of psychic ability which is further developed and enhanced by their years of training on Titan. While only a handful of Grey Knights Battle-Brothers ever achieve the levels of power commanded by the Chapter’s Librarians, they are all capable of manifesting certain powers and abilities, especially in the company of other Grey Knights where they can combine their gifts to create great effects and more devastating psychic attacks. However, those who prove to have a strength of mind far greater than that of their fellows will go on to join the ranks of the Chapter's Librarians. The Grey Knights have many abilities that standard Space Marines lack. These powers are psychic in nature and work on a gestalt principle much like that of the Orks in which the more Grey Knights that are present in one location, the more powerful their psychic abilities become. Besides these powers, the Grey Knights are highly-skilled close combat fighters. Most Grey Knights who are masters of melee combat are able to win against even the most seemingly impossible of odds. Unlike Space Marine Librarians or other psykers, their power is deemed free of the taint of the Warp and they are the only psykers allowed, for instance, in a Crusade army of the Black Templars Chapter.
Many Librarians are known to serve the Long Watch with the Chamber Militant of the Ordo Xenos, better known as the Deathwatch. Most of the Librarians called to serve in the Deathwatch hold the rank of Lexicanium, the most junior of the four ranks of the Space Marines' combat psykers. They are nonetheless warriors of fearsome ability and renown. However, a small number of higher-ranked Librarians do serve as the Watch Commanders' most valued counsellors. Within their own Chapters, Librarians may have different titles and unique methods of utilising their powers but they fulfill a number of similar roles within the Deathwatch. Chief amongst them is that of the combat psyker. By focusing his prodigious psychic powers, the Librarian is able to unleash withering blasts of searing Warp energy at his foe, reducing them to ashes with but a thought. Often, the energies are directed and multiplied through the blade of a specially crafted weapon such as a Force Sword or Force Halberd, with which even the mightiest of foes will be cut down as wheat before the scythe. Death can be unleashed from afar as well, for the Librarian is able to project his powers at distant enemies, launching deadly bolts of psychic energy from a staff, an outstretched hand, or through his very gaze. Unlike conventional weapons, a Librarian’s psychic wrath cannot be parried and does not run out of ammunition. The only limit on a Librarian’s powers is his own will, and this is as strong as that of any of the Imperium's mightiest heroes.
Librarians are also the guardians of the secrets of the Deathwatch. Within each Watch Fortress is to be found the sealed Vault which stores weapons and relics too dangerous to be allowed to fall into the hands of Mankind’s enemies. Also within the fortress' Vault is an archive of forbidden knowledge. Not even the Watch Commander has access to these archives -- only the Deathwatch's Librarians are entrusted with their access codes, and only they are judged strong enough to withstand the sanity-shattering secrets sealed within. It is only in the direst of circumstances that a Librarian will enter a Watch Fortress' Vault archive, for each time he does so he is exposed to the whispering voices of long-dead alien beings, tempting him with the power to rule the whole of humanity in the name of ancient and blasphemous gods. Nevertheless, so terrible are many of the horrors faced by the Deathwatch that the Librarian may be required to consult the archives in order to discover some previous record of an enemy’s weakness. Such knowledge can spell the difference between a mission’s success and failure.
Another role carried out by a Watch Fortress’ Librarians is that of providing the Watch Commander with counsel. Given their access to forbidden knowledge and their innate understanding of arcane matters, the word of a Librarian rarely goes unheeded in the Watch Commander’s plans. In addition to this, many Librarians are gifted with some degree of prognostication -- whether by way of visions, meditation,consulting the Emperor's Tarot, or seeming intuition, Librarians can often discern something of what will come to pass. Though such a premonition is rarely clear enough to provide complete certainty, it often provides clues that enable an experienced Librarian to make a sound judgement concerning potential dangers that may be faced in an upcoming mission, and to advise the Watch Captains accordingly. Often, the premonition focuses upon the actions of the Librarian himself, telling him that his own presence will be required if a mission is to succeed. Many Deathwatch Librarians have foreseen their own death at the hands of some alien monstrosity, and gone proudly and stoically to their fate, with certain knowledge that their death will sow the seed of their Battle-Brothers’ victory.
Another task at which many Librarians excel is the sending of psychic messages. Most Librarians are skilled enough to send telepathic messages from the surface of a planet to a vessel in orbit, and more powerful Librarians might even be able to contact a fellow Librarian in another sector. Generally, the further the message is projected in realspace, the less clear it becomes. However, in several cases, a Kill-team that has been considered to be lost has been recovered due to the efforts of a Librarian, who managed to invoke a simple insight from the mind of a Battle-Brother light years away. Given the nature of some of the places into which the Deathwatch must go, such an ability is invaluable, and has saved the lives of many of Mankind’s mightiest warriors. While many Deathwatch Librarians are, in effect, part of the Watch Commander’s officer cadre and not permanently assigned to a single Kill-team, in reality most come to associate themselves with one group of warriors. Such is the bond between the Battle-Brothers of a Kill-team that to separate them is to degrade their considerable combat effectiveness. Deathwatch Librarians are able to make a significant contribution to a Kill-team, lending their singular abilities to the eternal war against the alien horrors of the galaxy.
Within the Chapter, all Librarians hold a rank based on their level of training and their standing amongst their peers. In part these ranks indicate their principal role, be it on the battlefield or in the Librarium, but they are also used to establish a clear chain of command from the Chief Librarian down to the lowest Lexicanium.
- Lexicanium - A Lexicanium (plural: Lexicani) is a young Librarian who has generally not yet seen combat and is still learning to fully control and make use of his psychic powers. This is the lowest rank amongst a Chapter’s Librarians, awarded to those who have passed their trials and who are now deemed fit to serve the Chief Librarian. Reporting to the Codiciers, it is the Lexicanium's role to aid in the endless task of maintaining, studying and cataloguing the vast amounts of texts within the Librarium. In time of conflict, however, Lexicani will leave the Librarium and take to the battlefield alongside their Battle-Brothers, using their powers to smite their foes. In time, and with training and study, a Lexicanium will eventually rise in rank and take on a more active role within the Chapter as a Codicier. As Codicers they are often given more significant combat assignments, able to harness their powers with greater clarity. Lexicani are often distinguished by their lack of a Psychic Hood and helmet, and they usually appear very similar to their fellow, non-psychic Battle-Brothers except for the blue Power Armour that all Librarians are required to wear by the Codex Astartes as a sign of their status.
- Codiciers - Codiciers, like Lexicani, spend much of their time within the Librarium. They are tasked with organising and overseeing the efforts of the Lexicani, while reporting to the higher-ranking Librarians. By the time a Librarian reaches the rank of Codicier, his command of his powers is almost fully realised and only the truly gifted will advance beyond this point. However, a Codicier’s powers far outclass almost any other kind of psyker within the Imperium, and their psychic abilities are more than sufficient for the Chapter’s purposes. These Librarians have enough control over their psychic powers to go into combat. They usually receive further training to become Epistolaries, so they can use multiple psychic powers in combat. They also usually do not wear a Psychic Hood to augment their abilities, but rather devices more useful than that of their Imperial Sanctioned Psyker counterparts who serve in the ranks of the Imperial Guard.
- Epistolaries - While most Librarians never rise above the rank of Codicier, a few continue to develop their gifts and grow in strength until they attain the rank of Epistolary. Epistolaries fulfill two main roles within the Chapter: firstly as potent battle psykers who can combat the deadliest of foes, and secondly as psychic communications officers for their Chapter’s fleet. In this role they form the basis of the Chapter’s strategic command and control, directing fleets, coordinating mass planet-drops, and providing vital intelligence during invasions and assaults. These Veteran Librarians are powerful and their primary role, when not making use of their gifts on the battlefield, is that of the chief psychic communications officer of their Chapter. Even on the battlefield an Epistolary can send and receive psychic messages. Epistolaries have more mastery over their psychic powers than other, lesser-ranked Librarians, which allows them to use their abilities more often in combat than Codiciers or Lexicani. Epistolaries wear a Psychic Hood to augment their defensive abilities, carry a Force Weapon into combat and also have access to the full Armoury of their Chapter.
- Chief Librarian - The Chief Librarian is the strongest and most powerful psyker within a Space Marine Chapter, who all other Librarians in the Chapter report to, take instruction from, and respect. Few, if any, of the psykers within the Chapter will ever become the Chief Librarian. If there are no suitable candidates within a Chapter, the position is often left vacant. So rare are these psychic lords that many Chapters have but one or only a handful of psykers able to one day assume the responsibility of these mighty warriors. The Chief Librarian is the Master of the Librarium and the keeper of his Chapter’s lore, as well as a member of the guiding council of the Chapter's senior officers with encyclopaedic knowledge of his Chapter, its enemies, and the Imperium. The Chief Librarian presides over the training and selection of all new Librarians, as well as the cultivation of psykers within the Chapter’s ranks. He is also the closest of the Chapter Master’s advisors, providing him with wisdom and knowledge. His abilities to divine the future are vital to his lord’s decisions. Chief Librarians very seldom take to the field of battle, as their abilities are far more valuable to the Chapter in other ways. However, when they do take part in a battle, it is a glorious and terrifying sight to behold. With the power of their mind, they level fortresses, reduce entire armies to rivers of molten flesh, and split the very sky with fire and lightning. Chief Librarians often lead forces or assist the Chapter Master in battle. Chief Librarians also spend a great deal of time training their lesser Codicier and Lexicanium Battle-Brothers in the dangerous ways of the Warp.
Librarians are psychically-charged Astartes who are trained to use their abilities on the field of battle, as both weapons and as precognitive tools. The Librarians use a device known as a Psychic Hood to suppress their enemies' use of psychic powers and to augment their own; the hood's wires tap directly into the brain and act as an extension of the wearer's consciousness, allowing him to detect nearby manipulations of the Warp and to channel them through a series of crystals designed to augment the Librarian's willpower and thus make him more resistant to an enemy psyker's manipulations of Warp energy. When deployed, a Space Marine Librarian's psychic might exceeds even that of the Eldar Farseers in sheer brutality, though their abilities lack the sheer mental grace and accuracy that defines the fey Eldar species. Librarians wield potent Force Weapons, which are psychically-charged Power Weapons that allow the Librarian to enhance each strike with rippling psychic energy.
A Librarian of a Codex Astartes-compliant Space Marine Chapter wears blue Power Armour with the Chapter badge on the left shoulder plate, while on his right he has the Horned Skull or Open Book of the Librarium -- ancient and potent icons symbolising the power and knowledge that the Librarian possesses. Most wear a white robe over their torso which typically bears a stitched symbol of their rank (usually that of a Codicier or Epistolary). He will often wear a tabard or cloak of yellow bearing a black band, which is embellished depending on his rank. A Lexicanium’s band is untouched, while a Codicier’s has spikes or lightning bolts added to it, and an Epistolary has both spikes or lightning bolts and the addition of a skull placed below the band. Chief Librarians are a special case and often display symbols that reflect their own personal powers or honours dictated by their service to the Chapter. Most Librarians carry scrolls and copies of ancient texts with them, either as badges of office or as references of wisdom. Almost all Librarians above the rank of Codicier wear Psychic Hoods, the arcane apparatuses which contain crystals that can amplify the wearer's abilities and strengthen their control over them, as well as enhance their resistance to the psychic abilities of others.
Some Librarians go to battle in Tactical Dreadnought Armour -- better known as Terminator Armour -- which is painted and decorated in the same manner as their fellows clad in normal Power Armour, and also includes a Psychic Hood. Because of the sheer size of Terminator Armour, those suits worn by Librarians are modified to carry special Warp-sensitive crystals (similar to those fixed within Psychic Hoods) inside the finger tips and palm, so that a Librarian can still use his powers while encased within the protective suit. However, a Librarian in Terminator Armour may wish to simply use his Force Staff to manage and exert his power, and wield a ranged weapon in his free hand.
- Power Armour
- Bolt Pistol
- Force Weapon (of any type)
- Frag Grenades
- Krak Grenades
- Psychic Hood
- Bolter (as replacement for Bolt Pistol)
- Terminator Armour (as replacement for Power Armour, Bolt Pistol and Frag and Krak Grenades)
- Storm Bolter (if in Terminator Armour)
- Combi-flamer, -melta, -plasma or -grav (if in Terminator Armour)
- Storm Shield (if in Terminator Armour and using melee weapon)
Each Chapter has a Chief Librarian, the strongest and wisest psyker in the entire Chapter. A psychically-powerful Astartes often becomes the Chief Librarian by virtue of experience or by demonstrating exceptional self-control and willpower, both vital traits for an Imperial psyker. Below are named some of the most well-known Chief Librarians of the Space Marine Chapters of the Imperium of Man:
- Chief Librarian Tigurius - Tigurius is the Chief Librarian of the Ultramarines, a masterful telepath rumoured to be the most powerful of all known Adeptus Astartes psykers. It is said that he touched minds with the Tyranid Hive Mind and survived - a feat previously considered impossible, as the psychic weight of the Hive Mind would overload the telepath and subsume his soul. His equipment enhances the power of his psychic abilities, doubling their maximum range.
- Chief Librarian Mephiston - Mephiston of the Blood Angels not only survived the Black Rage, but also greatly benefited from it. His gaze is so terrible even the most disciplined heroes would quiver in his line of sight, and he possesses the ability to fly with his own power. He is a close-combat-oriented Librarian, and is perhaps the greatest Space Marine swordsman in the known galaxy.
- Grand Master Ezekiel - Ezekiel is the greatest of all Dark Angels Librarians and has the ability to traverse the minds of his enemies, predicting their moves before they even think of them. His Mind Worm psychic power can cause an opponent's brain to literally melt and the destroyed brain matter then leaks out through the ears.
- Hestion - This Librarian of the Salamanders Chapter played a valuable part in the first major conflict between the Imperium and the Dark Eldar in the 35th Millennium. He served on the Strike Cruiser Forgehammer when it was crippled by Dark Eldar raiders and taken through the Webway to Commorragh. With no means to call for aid, he saved the ship's complement by sending a psychic signal to the Astropaths of the Salamanders with the stricken vessel's coordinates. During the battle that followed in the Dark City of Commorragh, Hestion smashed many Dark Eldar gunships with a psychic storm and bought time for his Battle-Brothers to destroy the gravitic salvage spars holding the Strike Cruiser in captivity, allowing the Forgehammer to fly free again.
- Rune Priest Njal Stormcaller - While not officially a Librarian, Njal Stormcaller serves the Space Wolves Chapter as their most senior Rune Priest, the non-standard Chapter's closest equivalent. Njal earned his surname for his ability to summon potent storms through the power of his mind and the observation of the most ancient of Fenrisian shamanistic rituals.
- Jonah Orion - Jonah Orion is a powerful psyker who served as a Librarian of the Blood Ravens Chapter under Captain Gabriel Angelos, Commander of the Watch and leader of the Blood Ravens' 3rd Company, since the Tartarus campaign. During the First Aurelian Crusade, he was one of the Chapter's Librarians tasked with battling against the Tyranid Hive Mind of the encroaching splinter fleet of Hive Fleet Leviathan who had entered Sub-sector Aurelia intent on devouring all of its worlds. This bought time for Captain Gabriel and his Company to make their way towards Aurelia. While traveling through the Warp, Jonah would end up being the sole survivor of the dozen Librarians, Navigators and Astropaths accompanying Captain Angelos. Following this ordeal, Jonah's powerful psychic abilities would play an instrumental role in rooting out several pockets of Tyranid bioforms left over from the original invasion over the following year. During the Third Aurelain Crusade, Jonah would sell his life dearly, battling against the daemonically ascended and Chaos-corrupted Chapter Master, Azariah Kyras, upon the Dead World of Cyrene.
- Ahriman - Although not a Librarian of the Loyalist Chapters, the Chaos Sorcerer Ahriman was infamous for his journeys throughout the galaxy, ransacking vaults and looting any Chaotic or sorcerous artefacts he could get his hands on that would increase his own power or knowledge of the arcane. This caused many custodians of such artefacts, including several Space Marine Chapters, a great deal of paranoia and has resulted in the preemptive destruction of many artefacts to keep them out of Ahriman's hands. Ahriman is also responsible for turning the entire Thousand Sons Traitor Legion into mindless automata whose souls have been fused with their Power Armour through the use of the infamous spell known as the Rubric of Ahriman.
- Sarpedon - Sarpedon was the Chief Librarian and later, Chapter Master, of the Soul Drinkers, a Renegade Chapter of Space Marines that is currently considered Excommunicate Traitoris by the High Lords of Terra. Sarpedon possesses the unique psychic power known as The Hell that allows him to psychically enter and then project his opponents' greatest fears along with a recent physical mutation giving him extra appendages, manifesting in the form of chitinous spider legs which were unwillingly bestowed upon him by the Tzeentchian Daemon Prince Abraxes.
- Codex: Space Marines (7th Edition), pp. 17, 27, 39, 59, 61, 117-118, 131, 254-256, 292-294
- Codex: Space Marines (6th Edition), pp. 80, 165
- Codex: Space Marines (5th Edition), pp. 56-57
- Codex: Space Marines (4th Edition), pg. 17
- Deathwatch: Core Rulebook (RPG), pp. 182-200
- How To Paint Space Marines (Supplement), pg. 46
- Insignium Astartes, pg. 42
- Warhammer 40,000: Rogue Trader (1st Edition), Games Workshop, Nottingham, 1987
- Warhammer 40,000: Index Astrates - Volume I (Digital Edition)
- White Dwarf 326 (US), "Psykana Librarius - Space Marine Librarians in Warhammer 40,000", pp. 76-89
- White Dwarf 258 (US), "Index Astartes: Psykana Librarius, Space Marine Librarians"
- White Dwarf 227 (US), "Chapter Approved: Dark Angels - Ezekiel, Grand Master of Librarians", pp. 73-80
- White Dwarf 193 (US), "Dark Saviours: Dark Angels Characters - Ezekiel, Grand Master of Librarians, Keeper of the Book of Salvation, Holder of the Keys", pp. 91-95
- White Dwarf 166 (US), "Space Marines: Codex Imperialis - Librarians", pp. 8-19
- White Dwarf 145 (US), "Renegade: A Five-Part Campaign for Space Crusade - Campaign Background, Librarians", pp. 10-25
- Heroes of the Space Marines (Anthology), "Headhunted" by Steve Parker
- Dawn of War II - Chaos Rising
- Dawn of War II - Retribution