In the vast hall of the Imperial Palace on Terra, towering statues stand as testament to the Emperor’s twenty gene-forged sons – the Primarchs. Yet two pedestals lie conspicuously empty, their features erased and their names stricken from every record. These are the Lost Primarchs of the II and XI Legions, figures shrouded in absolute mystery and deliberately obscured by the Imperium’s own decree.
For centuries, their absence has been a source of hushed whispers and tantalizing speculation across the galaxy. What could cause the Emperor of Mankind, who engineered these mighty warlords, to purge all evidence of their existence? The tale of the Lost Primarchs is a blend of fragmentary official lore and the collective imagination of Warhammer 40K’s fanbase – a dark legend of “the forgotten and the purged” that continues to fuel the intrigue of the 41st Millennium.
The mystery of the Lost Primarchs sets a tone unlike any other in Warhammer 40K lore. In a universe where even gods and demons have detailed histories, the deliberate silence around the IInd and XIth Legions stands out. Within the setting, even mentioning these nameless brothers is taboo – an oath bound the remaining Primarchs never to speak of them.
Readers and players are left with only scraps of information from official sources, each hint spawning new questions. In this article, we’ll first recount what is known – the canon hints and scattered references that piece together a skeletal outline of the Lost Legions. Then, we’ll delve into the theories and speculation that fans have spun from those threads: who might these Primarchs have been, what fate befell them, and why their memory was condemned to oblivion. The journey begins with the facts as recorded in dusty Imperial archives and whispered by those few who dared acknowledge the Lost Primarchs’ existence.
Official Lore: The Forgotten and the Purged
In Warhammer 40K’s official lore, the Lost Primarchs are intentionally left as blank spaces – a mystery acknowledged but never fully explained. We know that the Emperor of Mankind created twenty Primarchs to lead twenty Space Marine Legions during the Great Crusade, each genetically engineered from his own gene-stock.
Over time, however, the records of two legions (the 2nd and 11th) were not just lost but purged from Imperial history. By the time of the Horus Heresy (the galaxy-wide civil war that nearly destroyed the Imperium), those two legions had already been erased from all official chronicles. Characters in the lore refer to them only obliquely.
We would be cast alongside the brothers we no longer speak of.
– Lorgar of the Word Bearers during the Great Crusade
For instance, during the Great Crusade, the Primarch Lorgar of the Word Bearers hints at their dire fate, lamenting “We would be cast alongside the brothers we no longer speak of” if he failed the Emperor. This chilling quote – “the brothers we no longer speak of” – confirms that by that point, the II and XI were cautionary tales, examples of ultimate failure.
Multiple sources establish that the two lost legions were gone decades before Horus’s rebellion. In the events at Monarchia (roughly 43 years prior to the Heresy’s outbreak), only 18 Legions are acknowledged as active, meaning the culling of II and XI had already occurred.
They are lost to us forever.
– Malcador the Sigillite, the Emperor’s regent
Rogal Dorn, Primarch of the Imperial Fists, muses during the Heresy that he wished those two legions were still around to aid the loyalists – only to be grimly warned “Do not even think it… They are lost to us forever” by Malcador the Sigillite, the Emperor’s regent. Dorn’s terse reply, “I know,” underscores that this loss is absolute and irreparable.
Even in the 41st Millennium, long after the Heresy, Roboute Guilliman (Primarch of the Ultramarines) remembers his missing brothers with a mix of regret and realism. “I was one of twenty. Two failed. Half the rest turned on my father. The Emperor is not infallible, nor am I,” Guilliman says upon his resurrection, bluntly acknowledging that two of the Emperor’s creations were complete failures. Yet he, like all loyal sons, refuses to speak their names or the specifics of their fall.
So what exactly is officially known about the Lost Primarchs? Frustratingly little. No names, no personal histories, no direct appearances in any story – only the aftermath of their erasure. It is clear the Emperor himself decreed their memory damned.
Magnus the Red once confirmed that the Emperor personally ordered the purging of the two errant Primarchs and their legions from all records. In effect, their existence became the Imperium’s darkest secret, a purge so thorough that even statues had their visages smashed. In one account, the Primarch Ferrus Manus discovers a hidden chamber of twenty statues – one for each brother – and notes that two stand shrouded with their faces obliterated.
Other sources refer to an “accident” that befell the lost ones, a shadowy precursor to Horus’s own treachery. Hints like these imply the lost Primarchs did something so abhorrent or tragic that the Emperor chose to eliminate all trace of them rather than let their deeds become public knowledge.
It is heavily implied that the Space Wolves, led by Leman Russ, played a role as the Emperor’s executioners in these secret tragedies. Russ earned the title “Emperor’s Executioner” for good reason. In the novel Prospero Burns, Russ grimly remarks – on the eve of being sent to punish another brother – that it wouldn’t be the first time his wolves had been unleashed against fellow Astartes.
This line strongly hints that Russ and the VI Legion were responsible for destroying one (or both) of the Lost Legions earlier in the Crusade. The Space Wolves were the Emperor’s sanction against betrayal or abomination within the legions, as later seen in their assault on the Thousand Sons.
Thus, many readers interpret Russ’s comment as a veiled reference to the prior censure of the IInd or XIth Legion, carried out in blood and fire by the Wolves of Fenris. Official texts stop short of confirming which legion Russ fought or why, but the context leaves little doubt that the Emperor did “loose the wolves” to make an example of those forgotten armies once before.
Another recurring detail in the lore is how the disappearance of the two legions coincided with a sudden surge in the size of the Ultramarines (the XIII Legion). Around the time the II and XI were expunged, it’s noted that the Ultramarines’ numbers swelled until they “eclipsed all of the other Legions”.
This has led to an in-universe rumor that the surviving Astartes of the lost legions were not executed, but rather folded into the Ultramarines as reinforcements, their original heraldry and identities scrubbed away. Characters in the lore discuss this possibility with skepticism – one Word Bearers marine calls it “insipid conjecture,” and others say it’s no secret that Guilliman’s forces grew enormously at that time.
If true, this would mean that it was the Primarchs themselves (and perhaps a few of their inner circle) who were judged guilty and purged, while the rank-and-file Space Marines of those legions were given a chance at redemption serving under a different Primarch. However, even this assimilation theory doesn’t explain the ultimate fate of the two Primarchs – whether they were executed, imprisoned, or met some other end is left unsaid. As one character wryly points out, “Those are just rumours”, underscoring that nothing about the Lost Primarchs is confirmed fact except their erasure.
The Horus Heresy novel series sprinkles a few other tantalizing references. In False Gods, the Warmaster Horus experiences a Chaos-induced vision where he observes the Emperor’s gene-laboratory and the infant Primarchs in their gestation pods. Horus pauses before the tank labeled “XI”, contemplating the “untapped glories that lay within, knowing they would never come to pass,” and in a fit of anger he smashes his fist against it.
Shortly thereafter, the Chaos Gods scatter the Primarchs across the galaxy. The symbolism of Horus damaging the XIth Primarch’s capsule is open to interpretation – was this an omen that the 11th would never fulfill his potential? Or even a causative act that somehow doomed that Primarch?
Likewise, in another tale, a Chaos-touched Word Bearer marine during a warp vision remarks that murdering the infant XIth Primarch at birth would “save them a lot of trouble” in the future. He speaks of unwriting “a shameful future,” implying that whatever the XIth Primarch eventually did brought great shame and required drastic correction.
All these snippets reinforce one notion: something went terribly wrong with the lost two, something apart from the Horus Heresy’s well-known betrayals. The Emperor and the remaining Primarchs deemed that failure so grave that the II and XI Legions had to be erased from history for good, their banners struck, their deeds unrecorded, and their very names consigned to oblivion.
Despite the secrecy, the Lost Primarchs cast a long shadow in the lore. The surviving Primarchs occasionally reflect on them with a mix of fear and regret. The fact that the Emperor could mutilate the Imperium’s own history to hide these “failed” sons adds a layer of tragedy to the grand narrative.
It suggests that even the Emperor, in all his ambition, miscalculated at least twice – raising the question of what mistakes were so dire that even he could not tolerate their memory. Official canon provides the setup: two legions gone before the great war, purged by the Emperor’s hand, possibly with Leman Russ as executioner, and rumors of their men folded into Guilliman’s legion.
But that’s where the factual account ends. Games Workshop has never revealed the names, personalities, or ultimate destinies of the Lost Primarchs in any official source. This deliberate silence has effectively passed the torch to the imagination of the fandom, giving rise to a host of theories and speculative tales over the years.
Theories and Speculation
What follows is not confirmed in any official text, but rather a collection of popular theories and imaginative speculation that fans have proposed to fill in the blanks. The mystery of the Lost Primarchs has inspired countless debates – some grounded in hints from the lore, others wildly creative. Here, we clearly separate these theories from canon, presenting them as possibilities that explore what might have happened to the IInd and XIth Legions.
Early Traitors (The “First Heretics” Theory)
One widespread idea is that the Lost Primarchs turned against the Imperium even before Horus’s rebellion. Perhaps they fell to Chaos corruption or launched some rebellion on their own during the Great Crusade. This is supported by the implication that the Emperor dealt with them personally and harshly, much as he would later deal with Horus – except their revolt was quashed in secret.
The phrase “the purged” suggests a deliberate cleansing, which could mean they betrayed the Emperor’s ideals and were destroyed for it. However, unlike the nine Traitor Legions of the Heresy, these two would have been expunged so early that few outside the Emperor’s inner circle ever knew of their fall.
Some fans speculate that one Primarch might have dabbled in forbidden lore or made pacts with foul entities, effectively becoming a proto-Chaos traitor. The Emperor, not yet willing to reveal the existence of Chaos to the nascent Imperium, would have hushed up the incident by wiping out the legion and sealing all records.
This theory casts the lost sons as unsung villains whose treachery never made it into the history books (or whose story was later twisted into legends of daemons and monsters). It’s a grim idea – that the Emperor’s gene-forging was flawed enough to produce traitors even without the Chaos Gods’ later temptations – but one that fits the ruthless logic of the Imperium’s censorship of history.
One Forgotten, One Purged (Tragedy Without Treason)
Another interpretation hinges on the nickname often ascribed to them: “the forgotten and the purged.” Some take this to mean two distinct fates – one Legion was “forgotten” (perhaps lost due to calamity or accident), and the other was “purged” (destroyed deliberately).
In this scenario, the IInd Primarch might have never properly joined the Imperium at all. For example, his capsule could have been lost in the Warp and never recovered, or he landed on a world that was annihilated before contact. That Primarch’s legion, lacking their gene-sire’s guidance, could have been disbanded or absorbed into others quietly – essentially written off as a failed venture without any great betrayal.
This would be the “forgotten” legion, lost due to misfortune rather than misconduct. The XIth, conversely, could be the truly “purged” one: a Primarch who was found and did take command of his legion, only to commit an unforgivable atrocity or display a fundamental flaw that led the Emperor to destroy him.
This atrocity need not have been outright heresy; it could have been something else unthinkable to the Emperor – for instance, genetic aberration. Some fans theorize a Primarch’s gene-seed mutation or uncontrollable psychosis could have driven his legion into madness or monstrous behavior, forcing the Emperor’s hand to purge them for the greater good.
In this telling, the lost Primarchs represent two different tragedies: one a victim of fate, the other a victim of his own hubris or corruption.
Execution by Russ (The Emperor’s Wrath)
Building on the clues in the novels, many believe that Leman Russ and his Space Wolves were dispatched to eliminate a wayward Primarch and his legion. The Space Wolves’ known role as the Emperor’s sanction suggests that when one of the Lost Legions strayed, Russ was ordered to bring them to heel – permanently.
Fans often imagine the saga of a great battle between Legions, with Russ reluctantly (or perhaps zealously) carrying out the Emperor’s wrath upon a brother who had gone astray. What might that stray Primarch have done to warrant extermination by his own kin? Speculations range from the mundane to the fantastical.
One possibility is that a lost Primarch embraced xenos – for example, making alliances with alien species to bolster his own power. Such an act would be blasphemous under the Imperial Truth (which demanded that humanity not worship gods and certainly not consort as equals with aliens).
A Primarch who defied this could be declared traitor. In the absence of Chaos as a known foe (this is before Horus’s heresy, after all), a Primarch turning xenos-lover or pursuing forbidden science (like dabbling in warp sorcery or abominable intelligence) would be a plausible cause for censure. Leman Russ, the staunch traditionalist and executioner, would have been the scalpel to cut out this cancer.
The theory dramatizes the brother-against-brother tragedy on a smaller scale before it played out in full during the Horus Heresy. It also gives weight to Russ’s own reflections; if he had already killed one brother, imagine the bitter taste when he was later sent to punish Magnus, and eventually saw half his brothers turn traitor.
In fan stories, Russ’s attack on a Lost Legion is often depicted as a somber, brutal affair that ends with the offending Primarch dead and Russ carrying a heavy burden of secrecy thereafter. This aligns with Russ’s character as described – he showed no surprise that Space Marines could be ordered to fight Space Marines, implying he’d seen it happen once before. As a result, some fans nickname the lost Primarchs “Russ’s redacted kills.”
Absorbed into Ultramarines (The Unseen Merger)
One of the most popular theories directly stems from that in-universe rumor about the Ultramarines. If the loyal elements of the Lost Legions were indeed merged into the Ultramarines, then it suggests that those Space Marines lived on under new colors, even though their Primarchs did not.
This theory paints a slightly less grim picture of the purge: rather than mass extermination, it was a forced reorganization and cover-up. The II and/or XI Legions could have suffered catastrophic losses (due to war or internal conflict) and been on the brink of destruction. The Emperor might have decided to spare the surviving Astartes but scatter them among more stable legions to prevent any legacy of their original command.
Guilliman’s Ultramarines, being exemplary in discipline and loyalty, would be the natural choice to receive these reinforcements. In practice, those Marines would have to abandon their old Legion identity – effectively becoming Ultramarines in name and heraldry – and the Imperium would erase their past from official records.
This would explain how the Ultramarines got so unusually large just before the Heresy. Fans who favor this theory often point to the Ultramarines’ later role in creating many successor Chapters; the extra manpower from two dissolved legions could be why Guilliman’s legion could spare so many troops to form new chapters after the Heresy.
As for the lost Primarchs themselves in this scenario, perhaps they were executed or secretly exiled, while their “sons” were spared to avoid waste. This idea has a certain appeal in that it meshes administrative logic (the Emperor reallocating resources) with the theme of shame and mercy – the Emperor might have pardoned the legions’ warriors by giving them a new start, even as he obliterated their former leaders’ legacy.
It’s important to note, though, that characters within the lore express doubt about this rumor. So, while intriguing, it remains one theory among many.
Exile, Survival, or Other Fates
Not every theory assumes the Lost Primarchs died. A more exotic line of speculation wonders if one or both of these mysterious figures could be alive, somewhere in hiding – deliberately kept away from the Imperium. Perhaps the Emperor did not kill a wayward son but instead exiled him to a distant world or imprisoned him in stasis, hoping to cure or redeem him later.
This is pure conjecture, but it resonates with mythical tales (like the fate of Angron’s brother Illidan in another universe, or the fate of Zahariel in 40K who was locked away beneath the Rock). An exiled Primarch might have been sent beyond the fringes of the galaxy or into the Eye of Terror as punishment.
If so, conceivably, such a being could return in a future storyline – a hook some fans dream about. Games Workshop has thus far shown no sign of introducing the Lost Primarchs in current lore, but the open-ended mystery means it’s not impossible.
Another survival theory posits that one lost Primarch and his legion might have deliberately sacrificed themselves to contain a terrible threat – for example, fighting a warp entity or xenos menace so dire that the Emperor decided their memory should be erased to prevent knowledge of that horror from spreading.
In this case, the lost Primarch could paradoxically have been a hero who did something so unspeakable (or fell victim to something so unspeakable) in the process of victory that the Emperor covered it up. This would make their “failure” not one of betrayal, but perhaps of being tragically tainted by the enemy they fought. While there’s no direct evidence for this in the lore, it’s a testament to the range of fan creativity that the lost Primarchs are imagined not only as villains, but sometimes as martyrs or monsters contained outside the normal narrative.
Fan Creations and Alternate Universes
Over the decades, the enigma of the Lost Primarchs has effectively invited fans to create their own legions and Primarch characters to fill the gap. Hobbyists designing custom Space Marine chapters have often joked that their army might descend from the “Lost Legion” to give themselves free creative license.
In fact, the original purpose of the missing legions in early Warhammer 40K development was exactly that – to leave room for players’ imaginations. This has led to some elaborate fan-made lore. Entire alternate history projects, like the popular “Two Missing Primarchs” discussions on forums, have given names and stories to the II and XI Legions.
For example, some fan writers have posited a Primarch of the IInd Legion who was a brilliant diplomat but fell victim to political intrigue, or an XIth Primarch who was female – a daughter of the Emperor – whose existence was hidden due to the Imperium’s sexism or the Emperor’s regret. (It should be stressed that there is no evidence in canon for a female Primarch, but it shows the extent of fan inventiveness.)
Others have tied existing mysterious chapters to the Lost Legions – the Blood Ravens from the Dawn of War series, with their unknown progenitor, are a frequent candidate for “secretly descended from a Lost Primarch” in fan theories. These ideas are all non-canon, of course, but they demonstrate how the blank canvas of the Lost Primarchs encourages the community to tell its own stories.
Conclusion
In the grim darkness of the far future, where every hero eventually becomes a tyrant or a corpse, the tale of the Lost Primarchs stands apart as a story untold – a void in history that tantalizes all who glimpse it. This deliberate mystery engineered by the writers (and echoed by the Emperor’s own actions in lore) has become a defining part of Warhammer 40K’s appeal.
By neither confirming nor denying the truth, the lore keeps the Lost Legions in a Schrödinger’s state of perpetual speculation. We know they existed, we know they were expunged for “good reason”, and we see the ripple effects of their absence in the paranoia and secrecy of the Imperium. But the full why and how of their demise remains locked away, like a classified file that even Inquisitors cannot access.
This aura of mystery undeniably adds to Warhammer’s enduring intrigue. Fans often cite the Lost Primarchs when talking about the depth of the universe – “There are secrets even we, the readers, aren’t privy to,” and that makes the setting feel even more vast and real. Every mention of the missing brothers in Black Library novels is electric, precisely because it’s so rare and so carefully danced around.
The Lost Primarchs also serve a narrative purpose: they are a reminder that the Emperor was fallible and that the Imperium has skeletons in its closet. As Guilliman noted, “Two failed” – a stark admission that even the Emperor’s grand project of the Primarchs had missteps grave enough to require deletion.
Their absence also amplifies the tragedy of the Heresy; if twenty had stood together, could Horus’s revolt have been averted or defeated more easily? We’ll never know, because two were missing from the board, and their strengths (or weaknesses) were lost to the Loyalist cause.
For now, Games Workshop has shown no inclination to fully unveil the Lost Primarchs’ story, and perhaps that is for the best. The mystery itself has become legendary. It gives hobbyists something to discuss endlessly, a puzzle with just enough pieces to form tantalizing shapes but forever missing the key pieces. It allows every player to indulge in a bit of personal head-canon – a corner of the sandbox where one’s imagination can run free without contradicting established lore. And it imparts a sense that in a universe so thoroughly documented in volumes of rulebooks and novels, there are still uncharted corners and secret histories waiting in the dark.
In the end, the Lost Primarchs exemplify a truth of the Warhammer 40K universe: that sometimes the questions are more powerful than the answers. Their legend endures precisely because it is unresolved – a shadowed chapter that whispers to us from the past, inviting us to wonder what could have been, and reminding us that some truths in the grim darkness will forever remain lost to time.
