Menes Kalliston was the Captain of the 4th Fellowship of the Thousand Sons Legion and a member of its Athanaen Cult during the Great Crusade and the opening days of the Horus Heresy in the late 30th and early 31st Millennium. Captain Kalliston led a squad of Battle-Brothers to the ravaged surface of their homeworld of Prospero to seek for any signs of survivors or their Primarch, Magnus the Red.
This occurred six solar months after the tragic events of the sanctioned Imperial campaign known as the Fall of Prospero played out. Imperial forces ravaged the Thousand Sons' homeworld following Magnus the Red's breach of the Emperor's Edicts of Nikaea, by flagrantly utilising the forbidden arts of sorcery.
A squad of the 4th Fellowship led by Kalliston was taken by surprise when they encountered a much larger force of Traitor World Eaters who were also on Prospero for their own nefarious reasons. In the ensuing conflagration, the majority of the squad was killed, and Kalliston was captured by none other than the infamous Assault Captain Khârn of the World Eaters' 8th Assault Company, who served as Equerry to the Primarch Angron of the World Eaters. Kalliston was subsequently tortured and later killed in a confrontation with Khârn. Only Revuel Arvida, a Sergeant of the 4th Fellowship and a member of the Corvidae Cult, managed to survive.
Throughout the Great Crusade, the psychically gifted Astartes of the Thousand Sons proved useful innumerable times as the XV Legion fought bravely in multiple campaigns, leaving few in doubt of their achievements. However, there were those Primarchs such as Leman Russ of the Space Wolves, Mortarion of the Death Guard and Corvus Corax of the Raven Guard who could never bring themselves to fully trust Magnus the Red and his Thousand Sons because of their own strong feelings against the use of sorcery and psykers in general.
Magnus saw the potential in exploiting the powers of psychically talented Astartes and was instrumental in the development of the Space Marines' corps of Librarians. The Librarians quickly proved to be loyal and effective warriors and soon acceptance by the Emperor and the Primarchs for their presence on the battlefield. Librarians soon became a powerful addition to the ranks of the Space Marine Legions.
However, there were those Primarchs who raised their voices in dissent, arguing amongst themselves and with the Emperor that Librarians should not be permitted within the ranks of the Astartes. Some desired to expand their Legions' Librarius and recruit even more Librarians into their ranks, whilst other Primarchs vehemently opposed the entire notion of Librarians and felt that they should be expunged from their ranks altogether.
Dismayed at the accusations leveled against Magnus and the friction the issue was causing amongst his Primarchs, the Emperor was also concerned about the Librarians and the dangers they presented to the Great Crusade when he was no longer fighting directly alongside his Space Marine Legions. Before departing for Terra to begin his secret Imperial Webway Project within the seclusion of the Imperial Palace's dungeons, he summoned the Primarchs and all the other major Imperial leaders to a War Council summit on the world of Nikaea to address the Librarian crisis.
Council of Nikaea
To solve this growing dispute over the use of psychic abilities once and for all, the Emperor summoned the Imperial War Council to the newly terraformed Frontier World of Nikaea to resolve the issue over the use of psychic powers in the Imperium of Man and so Magnus could rebut the charges of sorcery that had been laid against him. This great conclave, later known to Imperial savants as the Council of Nikaea, consisted of the Primarchs as well as Imperial officials drawn from all the various Adepta of the Imperium. The Emperor's judgement at the Council of Nikaea proved severe. With the exceptions of Navigators and Astropaths who were properly trained, controlled and sanctioned by the Imperium and were necessary to its continued existence, the Space Marine Legions were no longer to employ psykers within their ranks. The Emperor commanded that the Primarchs were to close their Librarius departments forthwith and not to indulge the undoubted psychic talents of those Asartes who possessed the gift. All existing Space Marine Librarians were likewise forbidden to make use of their abilities. The Council's rulings also created a new position amongst the Space Marine Legions, the Space Marine Chaplain, to uphold the Imperial Truth and help maintain the purity of an Astartes Legion's dedication and fidelity to the Emperor's commands.
Furthermore, Magnus was ordered to return to Prospero to reorganise his Legion, disband the Legion’s Librarius and redeploy its existing large corps of Librarians to the Legion's Battle Companies. The Emperor censured his use of psychics and dismissed Magnus with a final threat -- a fate that had also befallen the Lost Primarchs of the II and XI Legions: "If you treat with the Warp, Magnus, I shall visit destruction upon you. And your Legion's name will be struck from the Imperial records for all time."
Scouring of Prospero
Bitterly disappointed by the outcome of the Council of Nikaea, Magnus secretly raged against the Emperor and what he saw as his father's unjust ruling. Yet Magnus had no intention of giving up the promised power and knowledge of the Warp and continued to study the Immaterium and its secrets. He met with his senior Librarians and persuaded them to collude with his plan to secretly continue their studies of the occult and sorcery in secret. Following the Council of Nikaea, a recall order was astropathically transmitted to all of the XV Legion's far-flung Expeditionary Fleets, with the bulk of the Legion's number present on Prospero just before the Fall of Prospero. However, some of the Thousand Sons' Astartes had not arrived on Prospero when that world was assaulted. This would include those elements of the Thousand Sons such as Captain Menes Kalliston and his 4th Fellowship. The fate of these Thousand Sons Astartes untainted by their Legion's fall to Chaos remains unrecorded -- or deliberately excised -- from Imperial records.
The Warmaster Horus was being treated for the mortal wound he had sustained fighting alongside his Luna Wolves Legion against the Renegade Imperial Planetary Governor Eugen Temba on the Feral World of Davin within the Temple of the Serpent Lodge. Unbeknownst to anyone else in his Legion, the Warmaster's healing had been prearranged by First Chaplain Erebus of the Word Bearers so that the Chaos Cultists of the Serpent Lodge could transport Horus' soul into the Warp where he was seduced by the Ruinous Powers into betraying and challenging the Emperor for control of the galaxy. Magnus, meditating on Prospero, peered into the Warp with his one good eye and foresaw the pact with Chaos that the dying Warmaster had made to save his life. He also foresaw the epic events that were yet to unfold in the galaxy and could prove dire to the survival of the Imperium.
Burdened with the terrible information provided by this precognitive vision, Magnus gathered about him the secret cabal of his Legion's Sorcerer Librarians to discuss and interpret the meaning and implications of these dire portents. Troubled by the revelations of Horus' betrayal and the coming galactic civil war, Magnus risked further censure from his father by employing the use of a daemonic spell to warn the Emperor. Magnus' spell breached the protective wards and hexes around the Imperial Palace and penetrated into the subterranean levels of the Palace's dungeon deep within the earth. Enraged by his son's breach of his edicts, the Emperor promised swift and unrelenting retribution against the Thousand Sons Legion. He unleashed his executioners -- the Space Wolves Legion, upon the sons of Magnus.
Return to Prospero
Six solar months after the tragic events of the Fall of Prospero the sanctioned Imperial military reprisal against the Thousand Sons Legion's homeworld of Prospero, Captain Menes Kalliston of the 4th Fellowship led a squad of Battle-Brothers to the ravaged surface of their homeworld to seek for any signs of survivors or their Primarch. Instead, this squad was taken by surprise when they encountered a much larger force of Traitor World Eaters led by Assault Captain Khârn, Equerry to his Primarch Angron. The World Eaters were also on Prospero for their own nefarious reasons. In the ensuing conflagration, the majority of the squad was killed, and an unconscious Kalliston was captured by Khârn. When Kalliston finally came to, he discovered that he had been shackled to a chair, his innate psychic abilities severely weakened. He was interrogated by an individual who remained in shadow. Catching furtive glimpses of his tormentor, through bleary eyes Kalliston thought he made out grey-coloured Power Armour, and assumed that his captor was one of the hated Space Wolves Astartes who had destroyed his homeworld. Kalliston's tormentor desired to know the Thousand Sons captain's purpose for returning to Prospero.
Kalliston eventually realised that his tormentor’s armour, which he had thought to be grey in the near-total dark, was actually a dirty white. The shoulder guards were once a bright blue colour, though every exposed surface on the battle-plate was covered by a translucent layer of brown-red filth. His captor was a War Hound of the XII Legion, or, as he believed they had started calling themselves, a World Eater. To Kalliston the new name was ludicrous, a perversion of everything the Legiones Astartes stood for. As Kalliston's clarity returned to him, he slowly realised that his interrogator stood on the brink of madness. As he scrutinised his tormentor further, he could make out a series of iron studs implanted under the flesh, further up on the scalp. These neural implants, colloquially known as the Butcher's Nails, had been forbidden by the Emperor to be used by Astartes and had been prohibited for good reason. They accelerated an Astartes' aggression and stoked it, amplifying an already testosterone-charged superhuman killer into a truly savage murderer.
Kalliston realised he was in the presence of the savage Khârn, the Captain of the World Eaters' 8th Assault Company and Equerry to Angron himself. Withdrawing an iron pendant from his armour fashioned in the shape of a wolf's head howling against a crescent moon. Khârn explained to his captive that the World Eaters had come to Prospero on behalf of Horus to collect this item, known as the Moon Wolf. Once a part of the Warmaster's war plate, it had been used as part of a sorcerous ritual by the Thousands Sons' Primarch Magnus the Red to make contact with Horus, and could be used to do so again. But Kalliston quickly realised that there was another reason that the World Eater had come to Prospero, for Khârn seemed to burn with agony. An agony that could only be discharged by murder.
Biding his time, Kalliston goaded Khârn into revealing his true intentions. As the Thousand Sons captain pressed the agitated World Eater for answers, his psychic powers slowly began to return to him. Kalliston attempted to manipulate the situation by subtly swaying Khârn with his words and his innate psychic abilities. Kalliston realised that the World Eater had come to Prospero seeking certain arcane devices that might be able help him find a cure for his affliction. Kalliston explained to Khârn that there was still time. For though the sorcerous devices once used by the Thousand Sons had all been destroyed, he possessed the necessary knowledge to replicate their functions. He could help heal the World Eater's broken mind, remove the neural implants and restore his ebbing humanity. Kalliston could help take away the fire that drove him onwards, goading Khârn on to the acts of random violence he abhorred.
Kalliston knew that the World Eater was lost in a universe of pain, one that was only temporarily forgotten during the act of killing, a common affliction for those who fell to the corruption of the Blood God Khorne. He knew that his words had reached the sliver of Khârn's old self that still endured. But suddenly, the rage took over and Khârn snapped back to the reality of his painful existence. He attacked the Thousand Son captive with a roar, intent on rendering him limb from limb. Kalliston desperately called upon his remaining psychic reserves of power and managed to free himself from his bonds and launched a series of mental attacks against the enraged World Eaters officer. But it was all for naught, for the berserk Khârn possessed little of his remaining sanity and would not be persuaded by any means to stand aside from his intended kill.
As Kalliston was being pummeled to death, he reflected that he had given Khârn every opportunity to choose his path, and that when the murder and madness had finally subsided, he would have the leisure to reflect on this choice -- he could have turned back. Kalliston foresaw that in the near future, Khârn would be uncontainable, and would turn on whatever force had sought to channel his rage for their own purposes. None would ever master him, for he had lost mastery over himself and become a true mortal embodiment of the Blood God's unending thirst for death.
- Age of Darkness (Anthology), "Rebirth," by Chris Wraight, pp. 174-177, 179-183, 186-189, 193-195, 198-200, 205, 209