World Eaters - World Eaters Librarius: Before they were known as the World Eaters, like many of their fellow Legions, the War Hounds once maintained a dedicated Librarius Division made up of potent psykers who were highly talented, and trained to master the power of the Warp. But this changed with the rediscovery of their Primarch upon the world of Nuceria.The use of psychic abilities within the Space Marine Legions had become a heated topic of debate within the Imperium as some Primarchs had accepted the idea that the use of psychic abilities was beneficial to the Great Crusade's war effort in their own Legions, while others like Leman Russ and Mortarion refused to deal with what they saw as dishonourable deception and unnatural witchery and outlawed the use of all psychic powers as simply sorcery by another name.In His wisdom, the Emperor of Mankind invited advocates of both sides of the debate to a great Imperial conclave on the world of Nikaea in 001.M31. This was known as the Council of Nikaea, which would determine whether or not the use of psychic abilities represented a boon or a grave danger to Mankind and the newborn Imperium of Man.Ultimately the existence of psykers in the Imperium such as Astropaths and Navigators was allowed but tightly restricted under centralised Imperial control, while the potent and unrestricted use of psychic abilities that was defined as sorcery was officially banned.Additionally, the Emperor ordered the Librariums of all the Space Marine Legions to disband and the Librarians to be restored to the general ranks of the Astartes, making them swear an oath to never again use their psychic abilities. In the wake of the Horus Heresy, even this ban would ultimately be overturned  when the Loyalist Legions realised that the use of psykers was an essential weapon in the fight against Chaos.The newly renamed World Eaters utterly refused to heed, or even to acknowledge, the Edict of Nikaea. This was because by the time of the Council of Nikaea, their psychic kindred had already become an afterthought, scarcely worthy of consideration. Soon after the coming of their Primarch Angron, the World Eaters' psychic brethren were avoided and ostracised by all of their fellow Battle-Brothers.Non-psychic World Eaters would depart instinctively from their presence and spit on the floor before them, to ward off ill-fortune, a superstitious habit taken from Angron's homeworld, and one that had resonated throughout the XIIth Legion. Angron himself barely tolerated the psykers' presence.He instinctively mistrusted anything that was "unnatural," and hated psykers, feeling that his Legion would be clean only when the last of them finally died. This may have had something to do with the reality that when a psyker was in the Primarch's presence, Angron's neural implants would react badly, causing the Primarch extreme pain.Knowing how successful his own cybernetic neural implants had been at boosting his prowess and the prowess of his fellow Nucerian gladiators in battle, Angron had ordered his Legion's savants to study the neural implants known as the Butcher's Nails that he had been implanted with by his Nucerian slave masters. He instructed the Techmarines of the World Eaters to attempt to duplicate the process using the Primarch's own implants as templates to reverse-engineer the devices.However, this proved difficult, for Angron's implants were a relic of a long-lost human technology and little understood. Early attempts to duplicate these implants by the combined efforts of the Legion's Techmarines and Apothecaries proved far from successful, and resulted in high rates of mortality and homicidal frenzies erupting from test recruits. The World Eaters' first experiments with implantation of the Butcher's Nails in other Astartes proved less than pleasant.However, as time progressed, a viable form of the cortical implant technology was replicated and steadily improved, and soon the Butcher's Nails were implanted within the majority of the Battle-Brothers of the XIIth Legion. The Nails were not actually implants as Remembrancers and archeotechnicians understood the idea.The implants added nothing to a World Eater's brain. Instead, they stole from it. They bleached a warrior's mind of all reason, all caution, all of the instincts for survival that defined mortality.The Butcher's Nails rewarded rage with spurts of electrochemical pleasure, tingling synapses and deadening enjoyment of everything else. No better method for the pursuit of slaughter and murder had ever been contrived by the minds of men.But it soon became readily apparent that there was another problem with the Butcher's Nails implants. The first signs of unease came when implanted Librarians started causing their closest Battle-Brothers to suffer blinding migraines and debilitating facial bleeds. No Librarian could stand in Angron's presence without enduring the same thing themselves; a reflection of the torment they inflicted on their implanted brothers.But the depths of the flaws became truly obvious in battle. Librarians gifted with the Butcher's Nails lost the ability to control their psychic talents. One of them, a warrior attached to the 100th Company, had been lost to the madness created by the devices in his very first battle after implantation, and immolated three squads of the 100th Company when he could not cease projecting witch-lightning from his eyes.Several other implanted World Eaters Librarians had just...burst. They had combusted in pyres of flaming gore. More and more died -- none right away, but they never survived for long. In a single solar month, almost every Wold Eaters Librarian had been fitted with the Butcher's Nails. Mere weeks later, they all started dying.Optimism, albeit cautious, had reigned for a while. After the first deaths, the psychically trained Legionaries had sought to master the implants, to balance their sixth sense with the bionics now altering their brains' biochemistry. It was all just a matter of willpower they had said, and their Battle-Brothers had pretended not to notice the desperation in their eyes. It was all a matter of willpower -- yet the Librarians kept dying.The Librarians died in battle, in storms of fire or lightning, or -- in several incidents -- by pulsing hateful pain directed through the implants of nearby World Eaters warriors that forced their non-psychic kindred to suffer cerebrovascular blockages. Entire squads died of brain haemorrhages and strokes at their Codiciers' boots.Angron gave his psychic sons a choice between execution and the removal of their Butcher's Nails implants. The XIIth Legion learned, in those early years after their Primarch's rediscovery, that they had mutilated themselves in the image of a man without mercy. The Butcher's Nails could not be safely removed; every World Eater knew it, for the Emperor's own techno-mages had failed to remove the Primarch's implants after his recovery from Nuceria.Even so, most Librarians submitted themselves for the attempt. Every one of them died, without exception. With their rewired brains misfiring and enslaved to altered impulses, none of them died easily, and none of them died well. Soon enough, the last Librarians of the XIIth Legion were those who had not yet received the Butcher's Nails in a Legion now defined by the implants. The Librarians of the XIIth Legion came to eke out an isolated existence in the near-empty halls of their Librarius aboard the World Eaters flagship Conqueror.One by one these Librarians, too, began to die. Not from malfunction or misuse, but because they were World Eaters, and all World Eaters lived brief, violent lives. A hundred remained. Then fifty. Then twenty. No one mourned them. In a Legion that prized the bonds of front-line brotherhood above all else, the silent, psychic Battle-Brothers died alone -- never forgotten, but always ignored. Their gene-seed rotted with their bodies, unharvested in case their genetic legacy resulted in the same psychic curse infecting a second generation.Vorias, the eldest of the remaining Librarian coven and Lectio Primus of the XIIth Legion's Librarius Division had worked with the World Eaters Apothecarion and their senior attached Mechanicum Magi in trying to determine just why the Butcher's Nails reacted so poorly in the presence of psychic minds, but the line of research was abandoned when they had come to realise the context of their work: no one cared. No one but those cursed with a sixth sense. Besides, their efforts had always ended in vain, and killed too many "loyal" World Eaters who were unfortunate enough to be near the unstable Librarians.What followed was the gradual deterioration of any sense of brotherhood. With the death of kinship often came the death of loyalty, but the remaining Librarians were gene-born into the XIIth Legion and they would be World Eaters until the day they died. For the most part, the Librarians of the World Eaters did not hate their non-psychic Battle-Brothers for the way they were scorned, nor did they resent them for the way they spurned their talents as something dangerously worthless.They understood, only too perfectly, that their very presence caused their Battle-Brothers pain, and the XIIth Legion had no need of their psychic gifts. Even before the Edicts of Nikaea, such powers had never been factored into Angron's battle plans, as blunt and uncomplicated as those plans were. The Librarians had come to accept the truth beneath it all: they were not truly World Eaters. Their brothers were World Eaters, but they were still War Hounds. The XIIth Legion had moved on and left their psychic brothers behind to rot away within their ever-diminishing coven.By the beginning of the Horus Heresy in the early 31st Millennium, there were only 19 Librarians left within the entirety of the XIIth Legion. The few Librarians still living among the World Eaters by this time made valuable Battle-Brothers. They had come together as a coterie-squad, sharing power and silent words between their linked minds, forming among themselves the very brotherhood they were denied by the rest of the Legion. They considered themselves War Hounds rather than World Eaters on account of their lack of the Butcher's Nails. But their fate would soon be sealed upon the homeworld of Angron's youth.