Primarch

"They shall be my sons, and in them will live the hopes of a unified humanity. Theirs will be the strength to prevail, not only when victory lies within easy reach, but even when it seems unattainable, when doom settles like a shroud all about. In those times of darkness, my noble sons will shine the brightest of all."

- Attributed to the Emperor of Mankind

The Primarchs were the 20 genetically-engineered transhuman sons of the Emperor of Mankind created in the late 30th Millennium after the end of the Unification Wars. They were intended to be the immortal and superhuman leaders who would command the Emperor's Great Crusade to reunite the scattered human race beneath His leadership. Their genomes later served as the genetic templates from which the Emperor crafted His 20 Space Marine Legions. They were bred to be perfect generals, warriors and statesmen; larger, stronger, faster, and smarter than any normal human could ever hope to be. They possessed a charisma and martial prowess that made them like the mythical gods of old, untouchable by disease, old age or supposedly the petty failings of lesser men. The Primarchs were the Emperor's answer to reclaiming all the lost worlds of Mankind, and welcoming them into His new Imperium. The Emperor intended to raise His sons to be the best military commanders and political leaders Mankind had ever known, and they would bring the Imperial Truth to the rest of the human-settled galaxy in their father's name. Yet for all their gifts, the Primarchs were still men, and in the end their very human flaws would become the primary obstacle to the realisation of the Emperor's great dream for Mankind.

The Primarch Project
The massive scientific effort to create the Primarchs after the end of the Unification Wars in the 30th Millennium was known as the Primarch Project. The means by which the Emperor crafted 20 individual superhuman genomes using His own arcane Perpetual genetic code as the base without resorting to the use of cloning is unknown to present Imperial science. There was a 2-stage process involved: first, the Emperor extracted a subset of His own DNA to act as the foundation for a pure, undifferentiated Primarch gene-stock template. The pure Primarch gene-stock was then further differentiated into the 20 separate genetic templates that would serve as the individual Primarchs' genomes. The data concerning the original engineering of the individual Primarch strands was later analyzed by a Raven Guard Apothecary and a Magos Genetor of the Mechanicum during the Horus Heresy. They discovered that certain samples had gene sequences deliberately deleted from the base Primarch genome, while other samples showed the addition of clearly non-human DNA. Intriguingly, the genome of the Primarch listed as "Subject VI" had added canine-like DNA. Although it is not clear whether the sample numbers corresponded to the actual Primarchs of the numbered Space Marine Legions, this could explain the wolf-like affinity of Leman Russ and the unexpected feral mutation of many Space Wolves Astartes into the Wulfen.

It is believed by modern Imperial savants that there was more than just physical manipulation of the genetics involved in the creation of the Primarchs, and that the Emperor called upon many of the same techniques of psychic sorcery that had been used in His own creation millennia before by the shamans of Old Earth. It is also now known that sometime during the Dark Age of Technology, the man who would become the Emperor had travelled with several of His fellow Perpetuals, including Alivia Sureka, to the world of Molech, a Knight World only a few light years distant from Terra, in a one-way spacecraft. Sureka watched as the Emperor entered into a Warp Gate present on Molech, where he bargained with the powers of the Immaterium to gain new abilities and knowledge, including most likely the techniques needed to create the Primarchs. Sureka was later tasked by the Emperor with remaining on Molech to guard the Warp Gate and keep others from using it until His armies returned millennia later to conquer it for the nascent Imperium of Man during the early days of the Great Crusade.

This meant that the Primarchs were intended to be spiritually as well as physically engineered and may explain why the Primarchs possessed so much personal magnetism and charisma beyond what even their enhanced genetics would predict. But such arcane techniques also meant that the Primarchs were unusually vulnerable to the effects of Chaos since their souls would shine so brightly in the Immaterium and draw the attention of daemonic entities like moths to a candle flame. This is why the Emperor carefully inscribed arcane glyphs of protection on each Primarch's gestation capsule and around the gene-vault deep beneath the Imperial Palace in the Himalazian Mountains where they were created. Unfortunately, this protection proved insufficient, for the Chaos Gods learned of the Emperor's plans and the existence of the Primarch Project and decided they had no wish to see His attempt to weaken their power succeed by extending the grip of Order across the galaxy.

The Scattering of the Primarchs
The Ruinous Powers of Chaos somehow spirited the superhuman children away through the Warp, however, leaving them scattered across the galaxy. A massive localised Warp rift was created within the gene vaults of the Emperor's own palace, deep under the Himalazian (Himalayan) Mountains on Terra where the Primarchs were gestating. The gestation capsules containing the Emperor's unborn sons were scattered through the Warp to human colony planets long since lost to Mankind. It may have been at this time, when first touched by the hand of Chaos, that the first seeds of corruption were laid in the breasts of those Primarchs who would eventually turn Traitor to the Emperor and His Imperium. Whether the Emperor was able to affect this outcome is unsure, but every Primarch landed on ancient worlds of men, planets long since lost to the light of the greater universe beyond the stars. This was a massive setback to the Emperor's plans. He had counted on His superhuman generals to lead his army of conquest out from Terra. Without them, His plans, so many millennia in the making, rested on a knife's edge. He needed an edge, something to give Mankind an advantage as they struck out against a very hostile galaxy once more.

Despite this terrible setback, the Emperor was nothing if not adaptive, and He quickly developed another solution. Using the remaining samples of genetic material from each of His lost Primarchs, the Emperor crafted the first Astartes gene-seed, stem cell zygotes from which could be cultured genetically-engineered organs that, when implanted within a normal human male host, would allow that man to take on many of the physical and mental properties possessed by each Primarch. The Emperor implanted these organs into His bravest, strongest, and best human warriors whom He intended to stand by His side as the vanguard of the Great Crusade. Thus were born the Legiones Astartes, the Space Marines, and they would reconquer the galaxy for humanity at the command of the Master of Mankind. Although an Astartes warrior was but a pale copy of his Primarch sire, the technique of implanting human beings with extra organs allowed for a certain degree of "mass-production", and where the Emperor's 20 superhuman sons had been centuries in the making, thousands of Astartes could now be engineered and trained in the matter of a single Terran decade. These techniques provided the Emperor with the required numbers of warriors to successfully launch the Great Crusade in ca. 800.M30.

It should be noted that Adeptus Custodes gene-seed, which is apparently derived from the undifferentiated Primarch gene-stock, is more complex than base Astartes gene-seed, as it contains 12 more elements. The source of Custodian gene-seed, being only one step removed from the actual DNA of the Emperor Himself, may explain the Custodes' extremely heightened sense of kinship with the Emperor. However, the Custodian genetic code is still far simpler than each of the individual Primarch genomes, even though all were derived from the same source: the undifferentiated, pure Primarch gene-stock template.

Rediscovery of the Primarchs
As the new interstellar human empire expanded during the Great Crusade, the Emperor used His powerful gifts of psychic foresight and precognition to track down His wayward sons, scattered across the galaxy, and reunite them with their respective Space Marine Legions. Each Primarch was both a father and older brother to each Legion's Astartes, the source of that Legion's temperament and humours, a being in which each Legion saw its ultimate perfection and ways of war given personification. The return of the Primarchs to their Legions marked the height of the Great Crusade. First thousands, and then hundreds of thousands, of human-settled worlds fell to "Imperial Compliance," their conquest carried out by the newly reunited Primarchs and their Space Marine Legions. Like the gods of mythic Terran legend, the Primarchs strode the battlefields of the galaxy, and their power proved irresistible.

Yet the Primarchs, for all their expressed superiority and seeming immortality, were still men, and they possessed too many of the same human flaws that have bedeviled Mankind since the birth of the species. They proved jealous and arrogant, highly competitive and all-too-willing to hold grudges against one another and even their father the Emperor. Whether these flaws were the result of their exposure to the corrupting power of Chaos as infants or were simply the natural human flaws that could not be excised even from the progeny of the Emperor, is unknown. Yet, ultimately, it was the Primarchs' all-too-human flaws that doomed the Imperium to the nightmare of the Horus Heresy and 10,000 standard years of stagnation, decay, repression and endless war.

Order of Rediscovery of the Primarchs
The following is a definitive list of the order in which the Primarchs were rediscovered by the Emperor of Mankind during the Great Crusade starting in ca. 800.M30 as released by Black Library, the division of Games Workshop which is devoted to publishing all Warhammer 40,000 novels and audiobooks. This is the list that all future Games Workshop projects is likely to be based on, taking into account the most recent canon material from the latest novels used in the creation of this list.


 * Note of caution: Please bear in mind that there is a difference between a Primarch being found by the Emperor, and a Primarch taking command of their Legion.

Horus Heresy
At the height of the Great Crusade, the Imperial Warmaster Horus fell to the temptations of Chaos, and convinced eight of his fellow Primarchs to rebel against the Emperor and follow him in his attempt to supplant the Master of Mankind. During the Horus Heresy, brother fought brother as the fallen Primarchs led their Traitor Legions against their former comrades who remained loyal; Horus himself fought the Blood Angels' Primarch Sanguinius and the Emperor during the final battle of the great interstellar civil war. At the height of the final confrontation during the Battle of Terra, above the surface of Terra on Horus' own flagship, the Battle Barge Vengeful Spirit, the Emperor clashed with the Warmaster. The Emperor was reluctant to use His full power against His most beloved son, and it was not until Horus had mortally crippled the Emperor and killed Sanguinius that the Emperor finally utilised the full extent of his unimaginable psychic powers to bring the Warmaster down and eradicate even his soul from the Warp so that the Ruinous Powers could not restore him to some semblance of horrid life. Most of the remaining Traitor Legions fled into the Eye of Terror following Horus' defeat, and their Primarchs would sell their souls to Chaos, becoming Daemon Princes, each ruling a small Chaotic empire within the corrupted realms of the Eye of Terror.

The Loyalist Primarchs
Today, all the Primarchs are either damned in servitude to the Gods of Chaos, lost to current knowledge of their whereabouts or dead. As mentioned before, Sanguinius died at the hands of his beloved brother Horus, who in turn later died at the hands of his father, the Emperor. Ferrus Manus, Primarch of the Iron Hands, died on Istvaan V at the start of the Horus Heresy during the Drop Site Massacre. He was killed by his most beloved brother, the Primarch Fulgrim, who wielded the Silver Sword of the Laer, a daemonically-possessed weapon that was corrupting his own mind to Chaos and that later possessed him, to slay Ferrus. Fulgrim's body was later wholly possessed for a time by the Greater Daemon of Slaanesh who resided within the blade before the primarch reasserted his dominance and regained control of his body. Rumours abound that Ferrus Manus may currently still be alive on Mars as his body was restored to a semblance of life through the cybernetic assistance of the Adeptus Mechanicus. However the Mechanicus and the Iron Hands Chapter both fervently deny this speculation.

Over the next thousand years, the other remaining Loyalist Primarchs died or disappeared one by one. Lion El'Jonson of the Dark Angels returned to his homeworld of Caliban to find it in ruins, and the Dark Angel Space Marines he had left to garrison it were "corrupted" by the bitter Fallen Angel Luther to rebellion. He led a strike force of his own Space Marines against the Traitors on the surface, fighting with a burning hate towards his lost sons. The planet was heavily bombarded, drastically weakening it so that when the Chaos Gods realised they had failed to claim the Lion, they unleashed a Warp Storm of massive power and size. All that was left of Caliban's surface was the Tower of Angels and The Rock, the Dark Angels' former stronghold, with the rest being either destroyed or sucked into the Warp. When the Dark Angel Astartes got to the Tower of Angels, all they found was the unconscious body of Luther. The Lion was nowhere to be found. But some say that he is still asleep inside The Rock (the floating remains of Caliban turned into a Battle Fortress) with the Watchers in the Dark who are healing his injuries. Some Dark Angel Astartes say that he will return one day to lead them again. This would explain why Cypher, the Fallen Angel who has avoided capture time and again, has a special sword with him that he does not use in combat. This blade may be the Lion's own sword, amongst other possibilities, and the truth of its origins would be one of the first questions the Dark Angels would love to ask the most elusive of their Fallen brothers.

Jaghatai Khan of the White Scars disappeared through a Dark Eldar Warp portal whilst he was pursuing those savage xenos after a raid on the White Scars' homeworld. Rumours abound that he was captured whilst lost in the twisting paths of the Dark Eldar's section of the Webway.

Leman Russ of the Space Wolves is one of the Primarchs whose disappearance appears to be voluntary. The Space Wolves hold a legend that says Russ went on a quest to find a means to cure the Emperor with the fruit from the mystical Tree of Life, but the truth is likely to be far more complex. Others have said that Russ travelled into the Eye of Terror, to lead his lost 13th Company against Magnus the Red and the Thousand Sons Traitor Legion. Still other legends hold that Russ was dying and that he shall return when the Imperium most needs him, the period called "the Wolftime" to lead the Wolves of Fenris once more.

Rogal Dorn of the Imperial Fists died fighting on the bridge of the Chaos Despoiler-class Battleship Sword of Sacrilege alongside a company of his sons after he led a contingent of Imperial Fists in an attack on the massed armada of the 1st Black Crusade in the late 31st Millennium with a vastly outnumbered force. He had launched the hopeless assault in the hopes of delaying the Chaotic offensive upon the Imperium until reinforcements could arrive. He was one of the last Primarchs to die after the end of the Horus Heresy. His skeletal remains, weapons and Power Armour were recovered from the wreck, even as most of the Chaos starship was destroyed during the conflict. Today, Dorn's skeletal fists have been separated from the rest of his remains and are housed in the holiest shrine of the Imperial Fists Chapter onboard their mobile fortress-monastery the Phalanx, preserved in stasis for all time and inscribed with the names of every Imperial Fists Chapter Master to have led the sons of Dorn since his death. Only a Chapter Master has the right to inscribe his name and heraldry upon their sacred bones. At the same time, Dorn's skeletal corpse, without the hands, was also placed by the Imperial Fists within another chapel on the Phalanx, embedded within a block of clear amber that has been contoured to match the body's form.

Roboute Guilliman of the Ultramarines met his end slowly after fighting his former brother Fulgrim of the Emperor's Children Traitor Legion during the Battle of Thessala, following a slash across his throat with a corrupted Chaos blade which later poisoned him, the legendary Kinebrach Anathame that nearly killed his brother Horus.For ten thousand standard years, his body lay at the heart of the Ultramarines' Temple of Correction on Macragge, maintained in a stasis field to preserve it. He was the only Loyalist Primarch to still exist, in some physical sense, in the entire Imperium. His sons and billions of pilgrims every Terran year were able to experience the awe-inspiring sight of one of the Emperor's own sons, the bleeding wounds he sustained still visible upon his neck and chest. Legend among the Ultramarines holds that his wound is slowly healing, in spite of the impossibility of such a thing while in stasis. Guilliman was revived again after the fall of Cadia in the 13th Black Crusade during the Ultramar Campaign of 999.M41. Currently Guilliman serves once more as the Lord Commander of the Imperium and is leading the Indomitus Crusade in an attempt to throw back the Forces of Chaos and the xenos threats to the Imperium.

There is little known about how Vulkan of the Salamanders disappeared. He vanished into thin air around a thousand years after the Horus Heresy. Some claim that he died on Istvaan V, however he was later present at the Imperial Palace when Guilliman divided the Space Marine Legions into Chapters during the Second Founding. The Salamanders Chapter believes that after one of their number finds all nine relics that Vulkan left scattered around the galaxy for them to find, Vulkan will return to lead the Salamanders to victory against the Traitor Legions of Chaos and gain vengeance for the terrible slaughter suffered by the Chapter at Istvaan V.

Corax of the Raven Guard's end was tainted by guilt and shame. In order to rebuild the strength of his sons from the devastation of the Drop Site Massacre on Istvaan V, Corax sought to accelerate the growth of his Legion's gene-seed organs by obtaining a sample of the pure Primarch DNA from Terra that the Emperor had used to create his sons. The Emperor allowed Corax to carry out this mission and the needed genetic material was obtained, but infiltrators within the Raven Guard from the Alpha Legion used a daemonic essence to taint the Primarch DNA, causing many Raven Guard Aspirants to become hulking mutants. Filled with despair and shame at this outcome, Corax personally gave each degenerated Battle-Brother the Emperor's Peace. Riddled with guilt over what he had done to save his Legion, Corax locked himself away within his sanctum, the Raven's Tower, for a year. On the anniversary date of his self-imposed exile, he left his tower, haggard and gaunt, and took a small shuttlecraft. It was last monitored as setting a course for the Eye of Terror, the realm of the Chaos Gods. He left only a single word as his legacy -- "Nevermore".

Of all the Primarchs, excepting those missing or still present in unique conditions like Roboute Guilliman, only the damned Primarchs of Chaos live today, although their bodies, minds and souls have been completely consumed by the power of Chaos.

Traitors

 * The Warmaster Horus of the Sons of Horus was killed by the Emperor of Mankind aboard his own battle barge and flagship, the Vengeful Spirit, in orbit above Terra at the end of the Battle of Terra and his soul in the Warp was obliterated by the fully unleashed psychic power of the Emperor's mind. His corpse was later completely destroyed by the Chaos Lord Abaddon the Despoiler, who took Horus' place as the overall leader and Warmaster of the Forces of Chaos and the master of the Black Legion, the former Sons of Horus.
 * Magnus the Red of the Thousand Sons rose to become a Daemon Prince of Tzeentch and the master of the Planet of the Sorcerers within the Eye of Terror.
 * Angron of the World Eaters ultimately was transformed into a Daemon Prince of Khorne.
 * Mortarion of the Death Guard became a Daemon Prince of Nurgle.
 * Fulgrim of the Emperor's Children became a Daemon Prince of Slaanesh.
 * Lorgar of the Word Bearers served Chaos directly and so was transformed into a Daemon Prince of Chaos Undivided, the master of the Daemon World of Sicarus within the Eye of Terror, an unholy world dedicated to spreading the worship of the Ruinous Powers across the galaxy.
 * Perturabo of the Iron Warriors was also transformed into a Daemon Prince of Chaos Undivided.
 * Konrad Curze, also known as Night Haunter, was assassinated by the Callidus Temple Assassin M'Shen. He allowed her infiltration, apparently wanting to die to be freed of the stain on his soul imposed by his own life-long brutality.
 * Alpharius of the Alpha Legion was killed by Rogal Dorn. Omegon, who assumed the role of his Brother, was killed by Roboute Guilliman, but the source which reported his death may have been manipulated by one of the Legion's schemes. It is not known if Alpharius or his identical twin brother Omegon was the Primarch killed in the report. Due to the report's unreliability, the surviving twin may actually still live. The Alpha Legion may still be led by one of its Primarchs.

Loyalists

 * Ferrus Manus of the Iron Hands was killed at the Drop Site Massacre on Istvaan V at the start of the Horus Heresy by Fulgrim of the Emperor's Children who presented his head to Horus.
 * Sanguinius of the Blood Angels was slain by Horus on the bridge of his Battle Barge and flagship Vengeful Spirit in orbit above Terra at the end of the Battle of Terra and the siege of the Imperial Palace after refusing to join him and serve the Ruinous Powers of Chaos.
 * Lion El'Jonson of the Dark Angels returned to his homeworld of Caliban only to discover that his friend and second-in command Luther and the Dark Angel garrison left on their homeworld had turned against him and chosen to serve Chaos. He led a strike force of his own Loyalist Dark Angels against the Traitors, who were called the Fallen Angels. He disappeared amongst the inferno as the world was blasted apart by a Warp Storm caused by the Fallen Angels' adherence to Chaos and a powerful bombardment from his ships in orbit. He sleeps deep within the Rock, the biggest remaining piece of Caliban and the current mobile fortress-monastery of the Dark Angels. Only the Emperor and the Watchers in the Dark know of this great secret--a Primarch still lives.
 * Jaghatai Khan of the White Scars disappeared while pursuing Dark Eldar pirates into a Webway portal after they had managed to raid the world of Mundus Planus. There are rumours that he fights there still against the Dark Eldar, lost in the twisting paths of the Webway. After nine thousand years, it seems highly unlikely, but not impossible that Jaghatai Khan still lives.
 * Leman Russ of the Space Wolves disappeared into the Eye of Terror. The Space Wolves have a legend that says Russ went on a quest to find a means to cure the Emperor and restore him to full consciousness. His final words before his disappearance indicate that he would return during the Wolftime (the Last Battle between Order and Chaos). It is also said that Leman Russ led the 13th Company of the Space Wolves into the Eye of Terror and ordered them to hunt down the Traitor Legions which had fled into that vast Warp rift, particularly the Thousand Sons, the Space Wolves' most hated adversaries.
 * Rogal Dorn of the Imperial Fists died fighting on the bridge of the Chaos Despoiler-class Battleship Sword of Sacrilege alongside a company of his sons after he led a contingent of Imperial Fists in an attack on the massed armada of the 1st Black Crusade in the late 31st Millennium with a vastly outnumbered force. He had launched the hopeless assault in the hopes of delaying the Chaotic offensive upon the Imperium until reinforcements could arrive. He died long after many of his Loyalist brother Primarchs had already passed on. His skeletal remains, weapons and Power Armour were recovered from the wreck, even as most of the Chaos starship was destroyed during the conflict. Today, Dorn's skeletal fists have been separated from the rest of his remains and are housed in the holiest shrine of the Imperial Fists Chapter onboard their mobile fortress-monastery the Phalanx, preserved in stasis for all time and inscribed with the names of every Imperial Fists Chapter Master to have led the sons of Dorn since his death. Only a Chapter Master has the right to inscribe his name and heraldry upon their sacred bones. At the same time, Dorn's skeletal corpse, without the hands, was also placed by the Imperial Fists within another chapel on the Phalanx, embedded within a block of clear amber that has been contoured to match the body's form.
 * Roboute Guilliman of the Ultramarines was struck down with an envenomed Chaos blade by his brother Primarch Fulgrim. His body is perfectly preserved in a stasis field at the heart of the Temple of Correction on the world of Macragge. It is rumoured that he is still alive and that his wound is slowly healing, something considered physically impossible in a stasis field. The truth of this rumour remains unknown but this is seen by many (including the Ultramarines Captain Uriel Ventris) as mere wishful thinking. However, during the Ultramar Campaign in 999.M41, Roboute Guilliman was resurrected through a combination of the technical skill of Archmagos Dominus Belisarius Cawl and the psychic might of Ynnead, the Eldar God of the Dead, as directed through his priestess Yvraine, the leader of the Ynnari. After his awakening, Guilliman led the Terran Crusade to the Imperium's Throneworld to meet with his father the Emperor of Mankind for the first time in 10,000 standard years. In the wake of that meeting, Guilliman named himself the Lord Commander of the Imperium once more and launched the Indomitus Crusade to take the fight back to the encroaching enemies of Mankind.
 * Vulkan of the Salamanders disappeared. The position of Chapter Master, filled by the Captain of the 1st Company of the Salamanders ever since, is considered to be a regency as the Salamanders believe that Vulkan will one day return and lead them on a great crusade against Chaos.
 * Corax of the Raven Guard was racked by guilt and shame for what had happened to his Chapter when he had approved the use of heretical genetic manipulation in order to rapidly increase the numbers of the shattered Raven Guard after the Drop Site Massacre. In order to rebuild quickly the strength of his Legion from the Dropsite Massacre on Isstvan V, Corax had ordered the Raven Guard's Apothecaries to accelerate the growth of the Legion's gene-seed organs, producing more Space Marines than the process normally allowed, but these changes also degenerated or mutated the Legion's gene-seed, causing many Raven Guard Neophytes to become hulking, mutant monsters. Riddled with guilt over what he had done, Corax euthanised all of the mutated Astartes and then locked himself away within his sanctum, the Raven's Tower. Exactly one year later he left his tower, haggard and gaunt, and took a small shuttlecraft equipped with a Warp-Drive into the Immaterium with the words, "Never more." Corax's shuttle was last monitored setting a course through the Warp for the Eye of Terror. Corax's final fate remains unknown, though the Astartes of the Raven Guard and its Successor Chapters believe their Primarch still lives.

The Lost Primarchs
Almost nothing is known about the two unknown Lost Primarchs. References to the second and eleventh Primarchs are made in the short story, "The Lightning Tower," in which Rogal Dorn explains that the plinths on which their statues stand in the Imperial Palace should be vacant and says that "no one ever spoke of those two absent brothers. Their separate tragedies had seemed like aberrations. Had they, in fact, been warnings that no one had heeded?" The Traitor Primarchs' statues in this story are covered with a shroud, so the fate of the second and eleventh is undetermined. They may have been found and a tragedy befell them as the story implies they were spoken about posthumously.

During a conversation between Magnus the Red and Lorgar, it is mentioned that both Horus and Fulgrim upheld an oath taken never to speak again of the two lost brothers.

As for the fates of those Primarchs' Legions, speculation by the Word Bearers on "rumours" of a sudden swell in the Ultramarines' recruitment numbers following the decision to remove the two Primarchs from the Imperial record may indicate that some of the lost Legions' Astartes were integrated into the remaining Space Marine Legions.

Lost Future of the Primarchs
"While the Emperor had walked abroad, He had cloaked His manipulations in love. He had let His Primarchs call Him father; He had let them call themselves His sons. He had rarely spoken those words Himself, Guilliman now realised, and when He had He had done so without sincerity. Buffeted by the full might of the Emperor's will unclothed in flesh, a cloak had been ripped from Guilliman's eyes. The Emperor had allowed them to love Him, and to believe He loved them in return. He had not. His Primarchs were weapons, that was all."

- Personal contemplation of the Ultramarines Primarch Roboute Guilliman, Regent of the Imperium, sometime during the end of the first century of the 42nd Millennium

There has been intense speculation as to what the Emperor originally intended to do with the Primarchs if His plans had come to fruition and the galaxy had truly become an uncontested human domain in the wake of the Great Crusade. Unknown even to the Primarchs themselves, a vast underground cavern deep beneath the Imperial Palace had been designated as residential quarters for the Primarchs. There were 20 spacious apartments located there overlooking a large lake, with their design scaled for habitation by residents of the Primarch's massive proportions. At least one of the Primarchs, Corvus Corax, is known to have briefly stayed in his designated apartment during a visit to Terra at the beginning of the Horus Heresy.

The idea that all the Primarchs could be corralled into these residential quarters during an extended time of peace and prosperity after the Great Crusade had been successfully concluded was probably wishful thinking on the part of the Emperor. The Primarchs had been created for war, leadership and conquest -- they were great men intended to undertake heroic projects and a quiet life would have held little appeal for any of them. However, the Emperor kept both the physical infrastructure and knowledge gleaned from the Primarch Project intact -- including samples of the original generic Primarch gene-stock. These were kept in a secret, guarded location, and though dormant, they could have easily become functional again. Although the Emperor did not reveal why He was keeping these very sensitive assets, it suggests that He may have had further use for the genetic stocks and techniques used during the Primarch Project, perhaps related to peace rather than war. It is not known whether both the Primarch quarters and the Primarch Project laboratories in the Imperial Palace still exist. Additionally, the pure Primarch gene-stock sample was lost during the Horus Heresy after it was given to the Raven Guard and contaminated by a Chaos taint, and was then stolen by the Alpha Legion.