"Before we go, let me say this: I understand the conflict in your hearts, how one may beat for duty while the other bleeds for your Legion brothers who will be sacrificed. But this is civil war. It is a time of confusion, and realigned loyalty. We have many heads but we act as one – one Legion with a single will. We are a union of the alike and the like-minded. We will not tolerate treachery. We will not allow our compact to fracture. We will not suffer the short-sightedness of our brother Legions, nor the averted gaze of the wider Imperium. We are Alpha Legion and we take the long view."
— Omegon, twin-Primarch of the Alpha Legion
Alpharius Pythian Scales

An ancient Remembrancer's illustration of Alpharius, Primarch of the Alpha Legion during the Great Crusade, taken from Carpinus' Speculum Historiale

Alpharius Omegon (also known as the "Aleph Null," "The Hydra," the "Threefold Serpent," "The Final Configuration" and the "Last Primarch") was one of the twenty Primarchs created by the Emperor of Mankind in the earliest days of the Imperium of Man, just after the end of the Age of Strife in the 30th Millennium. In truth, Alpharius Omegon was actually a pair of identical twin brothers, one named Alpharius and the other Omegon. Of all the Primarchs of the Legiones Astartes, Alpharius was without a doubt the most steeped in mystery, legend, contradiction and deliberate falsification. The Primarch of the Alpha Legion shrouded himself in mystery, often moving unseen even amongst the ranks of his own Legion. However, when the time came to cast off the cloak of misdirection, Alpharius was as awe-inspiring a being as any of his other brother Primarchs. Clad in armour forged in the manner of some terrifying beast of ancient Terran myth and armed with a fearsome panoply of weapons of unknown provenance, Alpharius bestrode the battlefield like a figure from legend. Like the hydra he and his XXth Legion had taken as their symbol, Alpharius fought by repeated attacks from multiple and unexpected quarters. None could predict where or how the Primarch would strike, what weapons he would bring to bear or which of his many different forms would fight at his side. In many cases, the enemy were not even aware they were fighting the Alpha Legion until the very moment battle was joined, at which point they were already doomed to total and utter defeat at the hands of this most cunning, devious and duplicitous of all the Primarchs of the ancient Space Marine Legions.

Like the other Primarchs, Alpharius and his twin brother Omegon were transported from the Emperor's gene-lab beneath the Himalazian (Himalayan) Mountains of Terra through the Warp by the Chaos Gods and placed on a far-away world in an attempt to prevent the coming of the Age of the Imperium and the expansion of the ordered Imperium of Man across the Milky Way Galaxy. Alpharius Omegon was eventually rediscovered by the Primarch Horus and sent to meet his father the Emperor on Terra, who placed him (and secretly, his brother) in command of the XXth Legion, the so-called Alpha Legion, during the Great Crusade of the late 30th Millennium.

It should be noted that the Alpha Legion's trademark secrecy extends to the records of their Primarch. There is little recorded information on his biographical background or where his homeworld originates, and almost all of what is currently known by the Imperium about this enigmatic Primarch comes from the information provided by former Inquisitor Kravin of the Ordo Malleus. Inquisitor Kravin was subsequently believed to have been tainted by the Alpha Legion and his current whereabouts are unknown. Hence, much of the Imperial data concerning the Last Primarch could be considered suspect, and indeed there are some who believe the whole Kravin affair was an Alpha Legion plot to plant misinformation in Imperial records.

The greatest secret of the Alpha Legion's Primarch is apparently told to no one outside the XXth Legion, and has always been thus. For, unlike any of the other Primarchs, Alpharius actually has an identical twin: Omegon. It is unknown if the Emperor intended this when He created the Last Primarch, or was ever even aware that His final Primarch's engineered embryo had split into two identical fetuses during their gestation before they were stolen away by the Ruinous Powers. Alpharius and Omegon are both the co-equal Primarchs of the Alpha Legion, although "Alpharius" was the public face of the XXth Legion and appeared as the more senior of the two. Though as both Primarchs were physically identical it is possible for them to switch places and have "Omegon" play the public role of the Alpha Legion's Primarch. They have been described as "one soul in two bodies" and collectively have been referred to as simply "Alpharius Omegon". While the Astartes of the Alpha Legion made attempts to all look alike, both Alpharius and Omegon were still somewhat distinctive. Taller than the rest of the Legion, slightly copper-skinned, bald and possessed of a heavy brow, they somewhat resembled their brother Primarch Horus. Unlike him, Alpharius and Omegon had piercing eyes that seemed to glitter, appearing to shift colour from a cold arctic blue to a shimmering green. The overall impression given by Alpharius Omegon was one of nobility and intelligence. One way to tell the two twin Primarchs apart was when Omegon was serving as the commander of his Effrit Stealth Squad; large portions of his Power Armour and other gear were painted black and otherwise darkened. The armour worn by Alpharius was not particularly different from that of an ordinary Alpha Legionary. When such theatrics were required, both Alpharius and Omegon -- or one of their surrogates -- could appear as regally and stunning than any other Primarch.


The Hydra

Of the many mysteries that surround the Alpha Legion, the most fundamental and key enigma is the question of the Alpha Legion's Primarch, Alpharius. Of all of the Primarchs who remained to draw blood against each other in the Horus Heresy, of Alpharius the least is known for certain. Furthering this mystery and the outright deception perpetrated by Alpharius, many reliable accounts of his origins differ. One such account of the finding of Alpharius circulated secretly between the houses and factions of the Imperial Court on Terra, which states that his discovery was an accident of the Luna Wolves Legion prior to the end of the Great Crusade and the beginning of the 31st Millennium. By this, Alpharius was the leader of a confederation of human systems whose fleet of warships, no match in size or scale to Imperial vessels, managed through trickery and ambush to ingloriously lay low one of the outlying Luna Wolves battleships as it entered an unnamed star system. Responding to this unforgivable defeat, Horus himself and his fleet gave chase, only to find themselves mired in ambush after ambush, tricked into deadly traps and chasing shadows until Horus' own flagship, the mighty Vengeful Spirit, came under attack.

In the ensuing confrontation, the Luna Wolves smashed the enemy fleet's desperate attack aside, but in the confusion a single assassin broke into the flagship, and through stealth and murder managed the impossible task of fighting his way clear to Horus' command chamber and slaughtered his Justaerin bodyguards before Horus himself was forced to confront him. But Horus did not slay the attacker but recognised him instead for a brother. He had found the last Primarch! The new arrival called himself Alpharius and claimed to have been travelling this region of space for many years. However, he remained tight-lipped as to where he had come from. Various worlds in that locale were subsequently brought into the Imperial fold, but Alpharius always denied that any of them were his home of origin. The conglomeration of planets he had been leading was persuaded to join the Imperium with little bloodshed.

Another account torn form the mind of an Alpha Legion Centurion captured by the Legio Custodes after the Fall of the Seraphin tells the story of the finding of Alpharius. It speaks of a nameless Dead World at the edge of the Mandragoran Stars whose civilisation rose and was wiped out by bloody hands long before Mankind first walked on Terra. On this nameless orb, the nascent Primarch fell into the shattered ruins of a fallen city murdered long ages ago. Utterly alone, voiceless and without aid, he was forced to survive against the tortuous elements of the desolate world and the predations of the hungry ghosts of the charnel pit into which he had been consigned. His solitude was only broken after many long years by a new star falling from the heavens; a corsair ship of degenerate half-human renegades and alien mercenaries intent on plundering the dead ruins for whatever worth might remain amid the shatters. Instead they found only death at the young Primarch's hands, and Alpharius gained their weapons, their knowledge and their vessel as his own, and with it he set out in search of he who had made him.

Two other accounts, found encrypted within the pages of certain volumes of the suppressed work of memetic corrosion known as the Transit of the Human Soul through Strife, or the Codex Hydra as it is sometimes known, offer differing contentions. The first is that the lost Primarch was deposited on a thriving tech-oligarchy world known as Bar'Savor, but before his first decade of life there was done, the skies of Bar'Savor darkened as the nightmarish xenos worm-creatures known as the Slaugth descended to feed. Capturing the young Primarch, a being alone strong enough to resist them, the Slaugth kept Alpharius as a curiosity, twisting his mind with their horrors and enslaving him and tutoring him as a living weapon to sow strife and discord on their victim worlds before they fell upon them to feast.

It was the Emperor himself who at last liberated him, his gold Battle Barge ramming into the heart of the vast stone ship of the foul xenos to break it open, the Emperor's wrath like that of a vengeful god of legend in retribution for what had been done to his son. For long years after, Alpharius remained at his father's side as the Emperor undid what had been done to mar his creation. This account also offers a contradictory version of events, saying that Alpharius alone, unfinished in some way, had been spared or at least some part of him had remained behind though gravely injured when the rest of the Primarchs were scattered across the stars by unknown hands. Here, in the shadow of Terra, he grew and was nurtured alone of the Primarchs by the Emperor himself, his existence a jealously guarded secret even from those closest to the Emperor, lest the dark fates move against him. Upon his maturity he became the Emperor's own secret hand and his greatest shield, until he was at last parted from his father, his destiny to fulfill. It is unknown which one of these accounts are true and which are lies. The recorded facts suggest none of these accounts are real and they are but a few of the phantasms that purport to be the secret truth of Alpharius' past. Like the most potent of falsehoods, perhaps they contain a grain of truth within them, a hint at a greater secret yet.

The Emperor & Alpharius

Following his discovery, eventually Alpharius was taken back to the epicenter of the ever-expanding Imperium and reunited with his father, the Emperor. There was the usual rejoicing, pomp and circumstance, but records on Terra suggest that the two spent little time together. Alpharius was quickly sent to take command of his Legion, while the Emperor had many pressing affairs of state by this time. Alpharius and his twin-Primarch brother Omegon shared the same physical appearance and together served as joint-Primarch of the Alpha Legion. The Emperor was aware of Alpharius Omegon's secret; but whether the creation of the twin Primarchs was intentional or not remains a mystery. The two Primarchs supposedly shared one soul, with Omegon acting as Alpharius' second-in-command of the XXth Legion. The existence of the twin Primarchs of the Alpha Legion was known only to the members of the Legion itself, and was a well-kept secret even from the other Legions. The new Legionaries under their command were tall and strong, and were reminiscent of their Primarch, and possessed their gene-sire's cunning intelligence. When Alpharius Omegon took command of the XXth Legion, it was eager, zealous and completely committed to embracing the Primarch's command and combat philosophy. Alpharius led his Legion, created in his image, to the outer reaches of the Imperium and was eager to join battle and emulate the glories of the older Legions. In battle, this "youngest" Legion, driven by its mysterious and taciturn Primarch, became renowned quickly for its discipline and strict and impenetrable organisation and regime, which emphasised the unity of the Legion and its wider actions over the individual Astartes in every aspect. Its hallmark was a relentless application of force and a terrifying level of co-ordination between its warriors and war machines. This capacity for combined arms warfare, speed and surety of attack, were matched only by a mastery of the darker arts of war -- of sabotage and ambush, stealth tactics and assassination. Also evident was its desire for secrecy and talent for misdirection. It kept its distance from its fellow Legions, even when tasked to directly fight alongside them, and it is certain many fostered a sinister wilfulness, and beneath the facade, the shadow of mockery.

The Great Crusade

Fortronus Veteran Squad

The Alpha Legion conquering a non-Compliant world after conducting successful clandestine operations

Although its history as an active Legion is a short one compared to many -- at least under its own name -- the Alpha Legion proved quickly determined to match any of its brethren in glory -- or perhaps more accurately prove itself superior to them -- and its tally of victories mounted with surpassing speed. The Alpha Legion, ever watchful, was far from adverse from studying the strengths of their fellow Legions, and their weaknesses, and adapting the weapons and tactics of the other Legiones Astartes to their own ends. In this the Legion was not so different in strategic observances as the Ultramarines Legion and their master Roboute Guilliman, although it is doubtful that the Lord of Ultramar would have cared much for the comparison, even before the two Legions later came to bitter bloodshed. Such zealousness to prove themselves as part of the Great Crusade at any cost, and the often over-elaborate and needlessly complex and malign way in which the Alpha Legion chose to wage war, saw them quickly gain infamy more than fame. This, coupled with growing distrust due to their insular and deceptive nature, brought rivalry and acrimony between the Alpha Legion and much of the rest of the Legiones Astartes. As time passed, the relationship between the Alpha Legion and its peers soured further. The nature of the Alpha Legion's way of war and their lack of alliance to the commands of other Legions placed over them in the field brought Alpharius and his brothers Guilliman of the Ultramarines and Mortarion of the Death Guard into conflict on several separate occasions, with incidents notably occurring both in the aftermath of the Ullanor Crusade and a later campaign soon thereafter.

After Alpharius' disagreements with Roboute Guilliman over the supposed "dishonourable ways" of his Legion's chosen methods of warfare, the Alpha Legion threw themselves even further into their preferred method of operations, largely cutting themselves off from standard Imperial military practices and orchestrating greater and greater victorious examples of their approach to the Great Crusade, even when more conventional attacks would have been more efficient. The most notorious example of this took place on the world of Tesstra Prime, where the Alpha Legion, instead of taking the opportunity to capture the planetary capital city and thus force the world's surrender, allowed the enemy to dig in and defend it so that they could then expertly take the defending forces apart in a number of different ways. After a week of suffering seemingly random mishaps and deadly sabotage as well as brutal ambushes, the defenders were forced to capitulate, having taken 90% casualties. When asked why the XXth Legion had not taken the simpler strategy, Alpharius is reported to have replied that they avoided it as "it would have been too easy". This campaign brought Alpharius censure from almost all of his brother Primarchs. Guilliman in particular raged at Alpharius' conduct of the war, labeling the drawn-out operation as "a waste of the Emperor's bolt shells". Only the Warmaster Horus, always impressed by Alpharius and his work, praised the Alpha Legion's skill.

The Horus Heresy

Hydra's Eyes

A Chaos-possessed Alpha Legion Astartes during the Horus Heresy

It has long been supposed that since Alpharius was only familiar with one other Primarch, Horus, it was self-explanatory why he chose the side he did at the outset of the Horus Heresy. Indeed, the very plan at Istvaan V where Horus struck his first blow against the Loyalist Space Marine Legions by destroying most of the Iron Hands, Raven Guard and Salamanders Legions in a massive ambush, was very reminiscent of plans that Alpharius had created in the past. However, it is possible that there is another reason for Alpharius leading his Legion to the side of the Traitors, a secret known only inside the Legion. Approximately two years before the beginning of the Heresy, during the Compliance of Nurth, Alpharius Omegon was apparently contacted by members of a xenos organisation led by the Eldar but comprising an alliance of individuals drawn from a host of different intelligent species, called the Cabal, who brought to him visions of the impending civil war within the Imperium, and expanded knowledge of the nature and designs of the Ruinous Powers of Chaos. It is believed that the Cabal convinced Alpharius Omegon that the only way to permanently defeat Chaos in the galaxy was to ensure that Horus was victorious in his rebellion against the Emperor. It is perhaps for this reason that Alpharius Omegon, secretly true to the Imperium and loyal to the Emperor, may have chosen to join the Traitors who swore their souls to Chaos.

The Cabal, through its only known human agent John Grammaticus, explained that they had foreseen two possible outcomes to the coming Heresy. The first vision had the Alpha Legion remaining loyal to the Emperor and fighting against Horus, ending in the Emperor's victory. However, the Emperor would be gravely wounded and entombed inside the cybernetic sarcophagus of the Golden Throne, neither alive nor dead and no longer able to actively guide humanity. Ten millennia would pass and the Imperium of Man would be fated to slowly decay, until ultimately Chaos would return resurgent and defeat mankind, condemning humanity to eventual extinction. The second outcome had the Alpha Legion joining forces with Horus and Chaos Undivided and fighting the Emperor. In this vision, Horus was victorious and slew the Emperor. The Traitor Legions would defeat the Loyalists and Terra would belong to Horus, now the greatest Daemon Prince of Chaos. The vision continued with Horus, after slaying his father, shocked into sanity by his conscience and violently freed from Chaos' corrupt hold over him. Disgusted with himself and loathing what he had done, Horus would seek to exterminate the Chaos-corrupted human race in a vast orgy of bloodshed which would consume the entire Imperium in a single century. Though humanity would become extinct, the Chaos Powers would also be destroyed by the destruction of mankind, since ultimately their existence largely depended upon the collective psychic emanations of humanity in the Warp.

AlphariusOmegron Power Armour

Alpharius Omegon arrives on the world of Nurth

The Cabal, an alliance of xenos Eldar and a somewhat unwilling human psyker named John Grammaticus, burdened the Alpha Legion with these two visions which they promised would come to pass. The Alpha Legion were told the fate of the entire galaxy rested upon their Legion's decision alone. The Cabal had no time to reach or to attempt to convince another of the Space Marine Legions of what was to come. Either the Alpha Legion ensured the human race died in a century of incredible violence, sparing the other races of the galaxy, present and future, from Chaos forever, or they ensured the human race and the Imperium lived on for ten thousand years of bloodshed and decay, dooming the entire galaxy to brutal war and the eventual triumph of Chaos.

The Alpha Legion decided to join Horus' rebellion and made the decision that they believed the Emperor would have chosen, to sacrifice humanity for the ultimate eradication of Chaos from the universe. Yet their sacrifice seems to have been made in vain, as Horus did not find victory and the Imperium persevered despite the Alpha Legion's decision to support Chaos. This can only lead one to wonder if the Cabal and their future predictions were wrong, if the Cabal secretly served the interests of Chaos and lied to Alpharius simply to corrupt yet another Astartes Legion or if something else occurred that has yet to be discovered. It is noteworthy to mention that John Grammaticus, the human agent who made first contact with the Alpha Legion on the Cabal's behalf, was a man very similar to the Emperor himself. John was a powerful mutant psyker (known as a Perpetual) who had been alive for thousands of years, and had even met the Emperor face to face once, before the Emperor had finished uniting the various factions of men on Terra during the Unification Wars of the 30th Millennium.

The actions of the twin Primarchs during the Heresy proper are more than vague. Like other Legions and especially the Word Bearers, the many encounters with the Alpha Legion across several Sectors and Segmenta revealed that the XXth Legion had secretly built up their strength and was acting on different levels and in different warzones. It would then be logical to assume that both Primarchs would increasingly operate separately.

Deliverance Uprising

Following the Dropsite Massacre on Istvaan V, the mysterious Cabal sought to utilise the Alpha Legion in order to ensure Horus a swift victory. Following the calamitous events of Istvaan V and the Raven Guard's flight to Terra to bring word of the disaster, the shattered XIXth Legion returned to their home world of Deliverance. Unknown to them, the insidious Alpha Legion had inserted several of their own Legionaries, surgically disguised as Raven Guard Legionaries who had died on the black sands of Istvaan V. Gathering intelligence on Primarch Corax' efforts to reconstitute his Legion utilising a sample of pure Primarch DNA given to him by the Emperor Himself, the Alpha Legion operatives patiently waited until the Raven Guard had achieved a genetic breakthrough. In the meantime, they fomented rebellion amongst the old tech-guilds of Kiavahr, the Forge World that the moon of Deliverance circled, while assembling Alpha Legion forces nearby, for an unsuspected surgical strike. The Alpha Legion successfully tainted the Primarch DNA, which resulted in the disastrous mutation of newly inducted Raven Guard aspirants into hideously transformed creatures. At the same time, the Alpha Legion's plans reached their climax. The Kiavahr rebellion was well under way, supported by the newly arrived Alpha Legion forces, who were camouflaged as Raven Guard. The Loyalist Raven Guard successfully put down the rebellion and killed all the Alpha Legion operatives. In the aftermath of this successful operation, Alpharius was forced to oblige with handing over the obtained data research to the Emperor's Children's Chief Apothecary Fabius for further research. Unknown to Fabius though, was the data was practically useless and was incomplete at best. The Alpha Legion ensured they kept the integral data for themselves as well as the corrupted genome. Alpharius wished to utilise this valuable data to raise his Legion above all others. Following this action, Omegon met with the Cabal representative Athithirtir aboard his ship. After a terse exchange, the twin Primarch departed, informing the Cabal that the XXth Legion would fulfill its duties on its own without further external influence, interference or control.

Blockade at Chondax

Next, Alpharius later dispatched his forces in an attempt to blockade the White Scars from leaving the Chondax System and joining the Loyalist forces. The White Scars only became aware of the larger galaxy-wide conflict of the Horus Heresy, when Omegon initiated a mission to destroy Tenebrae 9-50, an asteroid facility that was being used as an Alpha Legion garrison. This Alpha Legion had been utilising a pylon array in order to jam any communications so that the White Scars would remain ignorant of the Warmaster's rebellion. Omegon despatched an Alpha Legion team led by Sheed Ranko on a one-way suicide mission to destroy the facility. It was later believed that the Alpha Legion possibly fabricated the claim that it was leaking information to their enemies and had therefore, become a liability. After the destruction of Tenebrae 9-50, the becalmed Warp become sedate, which allowed the White Scars to receive word of Horus's rebellion.

As the White Scars fleet made preparations to depart the Chondax System, they encountered a massive Alpha Legion flotilla. The Alpha Legion were an unknown quantity to the White Scars. They did not respond to communication requests and had hung back on the edge of the system, quietly accumulating more warships across a wide sweep of local space. There was no response from the XXth Legion's command despite all queries. All White Scars vessels were ordered not to escalate the situation and not to fire upon the interlopers unless fired upon. The warriors of the Vth Legion were to maintain perimeter integrity and not to permit Alpha Legion spacecraft to penetrate within range of the core White Scars fleet. Jaghatai ordered his fleet to prepare for immediate departure. As the White Scars' vessels began to move, the Alpha Legion reacted. They maintained the integrity of the cordon, warding the routes to the nearest suitable jump-points and keeping the White Scars corralled within the vicinity of Chondax. Utilising their superior drives of their vessels, and in an instant, suddenly switched from an aimless drift-pattern into an arrowhead shock assault of astonishing precision. Though both sides engaged one another, the White Scars made good their escape and fled the Chondax System.

Battle of the Alaxxes Nebula

Following the debacle at Chondax, Alpharius ordered the remainder of his fleet to beset the Space Wolves Legion at the Alaxxes Nebula. Leman Russ had ordered his battered VIth Legion to muster there in order to lick its wound after their recent campaign at Prospero, following the razing of the planet after the Thousand Sons had willfully disobeyed the Emperor's Decree Absolute. Horus had deployed the XXth Legion to launch a massive assault on Russ' battered and outnumbered Space Wolves. The Alpha Legion and its twin Primarchs, Alpharius Omegon, had long harboured deep grudges against the Space Wolves, and Russ in particular, for his criticism of their reliance upon trickery, manipulation and subterfuge to win battles rather than engaging in what the Space Wolves Primarch saw as honourable, open combat. The Alpha Legion relished the chance to prove their superiority against the arrogant Wolves of Fenris by delaying them long enough to keep them from contributing to the Imperial defence of Terra. Russ sent a distress call to the nearby White Scars, requesting that his brother Primarch Jaghatai Khan send his forces in order to assist the VIth Legion against the traitorous Alpha Legion. Unsure as to which side the Space Wolves truly belonged, the Khagan sympathised with his brother Primarch's predicament, but refused to get involved until he was able to sort out the conflicting and often contradictory astropathic messages he had received. Until he knew, beyond a shadow of doubt, who was ally and who was an enemy, he refused to choose sides. Wishing his brother the best of luck, Jaghatai wished to seek his answers elsewhere.

Realising that VIth Legion faced a hopeless situation, Russ was demoralised and isolated himself within his personal chambers, forcing his First Captain Gunnar Gunnhilt to assume command in his Primarch's absence. Harried at every turn, the Space Wolves' fleet faced imminent destruction by the larger Alpha Legion fleet, when suddenly, the Primarch reemerged from his chambers to lead his forces against the Traitor forces. During the height of the ensuing battle, a large contingent of elite Cataphractii Terminators of Laernaean teleported aboard the bridge Russ's flagship, Hrafnkel, where the Wolf King seemingly battled Alpharius disguised as one of his own Laernaean Terminators. As the Alpha Legion were on the verge of ultimate victory, help arrived from an unexpected quarter, in the form of a large Dark Angels fleet led by a mobile Ramilies-class Starfort, the Chimaera, who had heard the Space Wolves' distress signals and determined that the VIth Legion were in fact still loyal to the Emperor. With the assistance of their Ist Legion cousins, the Space Wolves were able to force the Alpha Legion to withdraw.

The Shattered Legions

Reliable testimonies of the Shattered Legions ship Sisypheum, most importantly the accounts of the Raven Guard specialist Nykona Sharrowkyn, place at least one of the Primarchs -- presumably Alpharius -- on a secret and hence unknown facility, designated as Lerna 2-12. In the disguise of the famed Iron Hands warleader Shadrak Meduson, Alpharius used the crew of the Sisypheum to assist in his hunt for Loyalist elements within the XXth Legion. His deception was only revealed towards the end of this affair, after the surviving members of the Shattered Legion force escaped with the knowledge that Alpharius had indeed been masquerading his Meduson.

The Solar Campaign

With its network of operatives and bondsmen, and women it is believed, that even in the state of civil war that the Imperium had fallen in, the Alpha Legion had the means and opportunities to transfer materiel and personnel between Sectors, including the Segmentum Solar and the strategically vital Sol System, whose defence had been entrusted to the Imperial Fists and their Primarch, Rogal Dorn, the newly proclaimed Praetorian of Terra. Under the tireless efforts of the Imperial Fists, the Sol System had become a fortress, each strata of the solar-system being turned into a perfectly organised defence zone to break the Warmaster's eventual assault. Given the Alpha Legion's tendency to prove its own superiority, it would not simply suffice to break open Terra's outer defences, but to humiliate the VIIth Legion, they would have to infiltrate the most secure location of the entire galaxy -- the Imperial Palace.

Alpha Legion units placed into enemy territory were trained and conditioned to pursue broad mission objectives in whatever way they thought best. The scope of these objectives were called mission parameters. An Alpha Legion force or warrior might have been given a series of potential mission parameters before its infiltration, some of which might be radically different in shape: killing or protecting the same individual, for example. Each parameter would have a single activation word or phrase that would set an infiltrator off towards a set of objectives. A word spoken down a vox or scrawled on a slip of parchment was enough to change the direction of their action from one parameter to another. And it was not uncommon for members of the same force to be following different mission parameters.

Activating assets that had been dormant and hidden on Terra for several decades, the Alpha Legion would eventually succeed where all other had failed before, infiltrating several agents within the Imperial Palace and especially the Investiary, where great statues had been erected to commemorate the Great Crusade's greatest generals -- the Primarchs of the twenty Legions. Two plinths had stood empty for a long time, the statues adorning them destroyed when their respective owners were cast to oblivion and their history erased -- the Lost Primarchs, but the nine statues of those Primarchs having turned against the Emperor had merely been covered up. This was to be the Alpha Legion's target. Infiltrated Legionaries succeeded into penetrating into the Investiary and destroyed all the statues except two of them -- those of Alpharius and Rogal Dorn. Intended as both a challenge and a message, this feat was deliberately kept secret from the other organisations within the Imperial Palace, even the Regent of Terra, Malcador the Sigilite, and the Emperor's own bodyguards, the Legio Custodes, were forbidden to enter the Investiary and witness the shaming of the Imperial Fists. By what means the Sigilite still discovered the presence of the Alpha Legion on Terra remains a mystery, but Rogal Dorn was adamant that he would deal with the treacherous XXth Legion in due course. Shortly after this act of sabotage an Alpha Legion fleet, led by Harrowmaster Kel Silonius, attacked the Sol System's outermost defences, and managed to even capture several of Pluto's moons, which constituted the heart of the outermost defence perimeter. What truly occurred there remains a well-guarded secret, one only kept by Rogal Dorn himself and his Huscarl-bodyguard.

The Battle of Pluto

In order to prepare for Horus' advance towards Terra, the Alpha Legion was charged by the Warmaster to carry out vital acts of sabotage and preparation, which would plunge the Solar System into complete chaos. Though heavily defended by the Imperial Fists Legion, led by the Praetorian of Terra, Lord Dorn himself, the Primarch Alpharius, aboard his flagship Alpha, led his fleet towards the Sol System. He managed to successfully infiltrate the outer defences of the system by putting himself, and the entirety of the personnel within his fleet, into stasis. Meanwhile, the Alpha Legion fleet approached at minimum speed and powered down to bare minimum, in order to reduce their overall heat signature. Thus it took an entire year for the Alpha Legion fleet to drift towards Sol and successfully reach the outskirts of Terra's defences undetected, as Warp travel had been strictly forbidden.

Meanwhile Alpha Legion Sparatoi (augmented and highly adept human agents) as well as Alpha Legion operative teams activated throughout the Sol System. These 'sleeper' cells had been planted years earlier before the outbreak of the Horus Heresy, and upon activation, performed their primary functions of sowing destruction and diversionary terrorist acts, causing panic and anarchy. Multiple acts of murder and sabotage were conducted on multiple planets to distract the beleaguered Imperial defenders from the Alpha Legion's true objective -- Pluto -- the lynchpin of the Loyalist's surveillance network within the Sol System. As Lord Dorn was distracted by this diversionary attacks across the system, Alpharius' fleet, comprised of over 200 vessels, led by the Alpha, struck Pluto and its moons Charon, Kerberos, Nix, Styx and finally Hydra. As the fleet arrived, further uprising, instigated by Alpha Legion teams, erupted across the Sol System.

The Alpha Legion's primary objective was Hydra, a fortress moon that orbited Pluto, that was a major Astropathic monitoring station. Alpharius himself, led a team of Alpha Legion warriors in the attack on the moon. Meanwhile, the Loyalist defenders, led by First Captain Sigismund, had just 30 ships to defend against the massive Alpha Legion fleet. Due to the unexpected and brutal assault, the severely outnumbered Loyalist fleet was badly mauled by Fire Ships hidden among the Alpha Legion fleet, to wreak havoc on the Imperial Fists defenders. The captured fortress moon of Kerberos rained down deadly fire upon Charon, Nix, and Styx with heavy fire. Despite facing overwhelming odds, the Imperial Fists resolutely stood their ground in the face of the Alpha Legion's overwhelming assault.

Death and Rebirth

Dorn vs. Alpharius

Alpharius and Rogal Dorn confront one another, one last time, during the Battle of Pluto.

Meanwhile, Archamus, Lord Dorn's Master of the Huscarls, was eventually able to deduce the Alpha Legion's true intentions -- to sabotage Hydra. During the fighting, Archamus led a Huscarl contingent in a daring assault upon the Alpha Legion force led by Primarch Alpharius himself. In the subsequent fighting, the Huscarls were killed and Archamus was left mortally wounded. All seemed lost, as the battle seemed to swing in favour of the Traitor forces. But miraculously, the Imperial Fists' mobile star-fortress Phalanx, led by Lord Dorn himself, arrived with a massive Imperial Fists fleet in tow. They were boasted with additional reinforcements from the Armada Imperialis. Utilising the competing gravity wells throughout the Solar System, the Imperial Fists fleet managed to arrive quickly by slingshotting itself towards Pluto. The Imperial Fists reinforcements immediatley pacified the captured guns on Kerberos, as Lord Dorn led in Huscarls in an assault upon the astropathic chamber on Hydra.

Dorn and his remaining Huscarls teleported directly into the locked chamber, and soon joined battle against Alpharius and his elite Lernaean Terminators. Archamus looked on helplessly, as the two Primarchs fought one another in an epic life-or-death duel. When Alpharius was about to impale Dorn with his Pale Spear, the now-dying Archamus grabbed the hilt of the weapon and deflected it harmlessly into a non-vital area of Dorn's chest. This gave Lord Dorn the opening he needed, to grab the weapon's hilt, and using his deadly Chainsword, Storm's Teeth, he sliced through Alpharius' wrists, severing his hands from his arms, before slashing his former brother across his chest, and then impaling him with his own spear. Finally, Lord Dorn finished off Alpharius with a deadly chop of his mighty chainsword into the top of his skull. With the death of their Primarch, the Alpha Legion fleet withdrew and retreated from Pluto. At the moment of his twin-Primarch's death, Omegon sensed the death of his sibling and became distant. Shortly thereafter, he was notified that the Warmaster demanded that Alpharius speak with him so that he could know the status of the Alpha Legion's attack on the Solar System. Like he had done many times before, Omegon immediately took upon himself, his brother's name, and permanently assumed the mantle of Primarch of the XXth Legion.

During the remainder of the Heresy, the Alpha Legion split off from the main body of Horus' forces early and did not attack Terra with the majority of the Traitor Legions, instead embarking upon a series of delaying actions in an attempt to hold potential Imperial reinforcements for the defence of Terra in place. They also engaged in smaller actions, defeating a White Scars force on Tallarn and a Space Wolves unit at Yarant. Despite their contributions, however, Horus was ultimately defeated by the Emperor aboard his battle barge at the end of the Siege of the Imperial Palace on Terra.


During the Horus Heresy, Alpharius Omegon appeared more interested in proving his own Legion's worth by fighting, at every chance he got, the best of the Loyalist Legions. In the aftermath of the Horus Heresy, the Alpha Legion did not retreat to the Eye of Terror like the other Traitor Legions; instead they moved on to the galactic East, following new objectives of their own devising. Whether or not being brought to battle with the Ultramarines was one of these objectives is unknown, but it occurred all the same. It was on the world known as Eskrador that Alpharius and Roboute Guilliman would meet for the last time. Believing that Guilliman would adopt his standard deployment procedures as later outlined in the Codex Astartes, Alpharius was surprised by the Ultramarines, as a splinter force including their Primarch made a quick strike at the Alpha Legion's headquarters. Alpharius was reportedly happy with such a development, as it allowed him to demonstrate the superiority of his flexible, multitudinous and unexpected military strategies over the notoriously precise, methodical and perhaps even tactically moribund Ultramarines. Both Primarchs met in combat and Alpharius was killed. Believing the combat over, for what Astartes Legion could ever survive the loss of their Primarch in battle, the Ultramarines were taken by surprise by the remaining elements of the Alpha Legion, when they struck back a day later. The Ultramarines who had launched the attack on the Traitor Legion's headquarters were harried so mercilessly that by the time they had returned to the main body of the Ultramarine force their casualties were almost total. After a week of constant fighting and heavy losses, the Ultramarines' strike force managed to reunite with their main elements, and quickly evacuated the planet. Even though they had lost their Primarch, the Alpha Legion had soundly beaten the Ultramarines, who proceeded to bombard their foes' position from orbit. It should be noted, however, that Alpharius' death is still considered suspect even by the Ultramarines, and he may still be at large. On the other hand, it is possible that "Alpharius" did indeed die and his twin "Omegon" took sole command of the Alpha Legion.

Unlike the other Traitor Legions, most of the Alpha Legion does not reside in the Warp, but rather roams the galaxy in warbands of warriors, each of which is trained to act independently of each other in pursuit of their greater cause. In this way the Alpha Legion was by and large the only Traitor Legion not to succumb to the mutations of Chaos, an outcome that may also have been dictated by their continued secret loyalty to the Emperor of Mankind.

Following the Battle of Eskrador, the Alpha Legion fractured in order to hide from the Imperium. Small, autonomous warbands were left in Imperial space where they set up secret bases in asteroid fields, Space Hulks, and barren, unpopulated worlds. These units launched frequent attacks against military targets that were weakened by the Heresy and even today still pose a threat to Imperial starships, settlements, and garrisons. The Alpha Legion's warbands also spread and coordinate Chaos Cults throughout the galaxy in order to instigate massive planetary revolts against Imperial rule. These insurrections are often used to lure Imperial forces away from worlds the Alpha Legion wants to attack, paving the way for large-scale assaults of Chaos Space Marines from the Eye of Terror.

The Alpha Legion's role in spreading heretical Chaos Cults across the Imperium has earned them the loathing of the Inquisition, whose Ordo Malleus and Ordo Hereticus have devoted considerable resources to finding and destroying their secret bases. The Alpha Legion has been declared wiped out by the High Lords of Terra no fewer than three times, in the 31st Millennium, the 32nd Millennium and the 39th Millennium. These claims have always been disproved by the continued assaults of the Legion. The Alpha Legion has suffered heavy casualties on many occasions since the end of the Heresy, yet its continued large numbers has led many Imperial observers to conclude that they are recruiting new members into the Legion and thus have managed to maintain a supply of untainted gene-seed, also a rarity for Chaos Space Marines.


Contemporary accounts record Alpharius as a masterful tactician and strategist whose skills were rated by the Imperial Stratagos as akin to the legendary abilities of the Iron Warriors' Primarch Perturabo or the Ultramarines' Primarch Roboute Guilliman. His erudition was said to be astounding, but one whose great intelligence was as cool and as watchful as a viper's gaze. His is recorded as having sought out the comradeship and council of none of his brother-Primarchs save perhaps Horus, although some reports that place him also on Caliban, home of the Dark Angels' Primarch Lion El'Jonson, and Terra at various times cannot be easily dismissed. He is said to have encouraged his commanders to operated with extreme independence of thought and action, and yet the Alpha Legion was known to pride itself on its unbreakable unity of purpose and will. Such are the paradoxes that abound in the wake of the shadowed figure of Alpharius, and in this he can be said to encompass his Legion.

Physical Traits

Furthering the mystery of the Alpha Legion Primarch and the outright deception perpetrated by Alpharius, many reliable reports of the Primarch's physical appearance differ. While he is noted on many occasions to be of similar stature and countenance of many of his Legionaries and able to pass unnoticed in their ranks, other records show him as a towering and fearful figure as were the other Primarchs, bedecked in a sinisterly ornate, hydra-chased battle plate and wielding a mighty double-headed spear. There was a certain likeness in the cast of features to both Horus Lupercal and the face the Emperor wore, which made sense if the gene-legacy theory was true.


  • The Pythian Scales - Although frequently recorded as entering battle in the semblance of a regular member of his XXth Legion, Alpharius -- or perhaps an individual carrying that name -- was also known to have led his Legion to war armoured in sinister and baroque reptialian-styled Power Armour whose stature left no doubts in the mind of onlookers that a bloody-handed Primarch had entered the fray. This armour, faceless and fashioned after the style of the shadowed mythic age of Ancient Terra, was known as the Pythian Scales, and could turn aside blade, energy blast and alchemical attack with equal ease.
  • Venom Spheres - Venom Spheres were specialised assault grenades utilised only by the Alpha Legion. This deadly weapons upgrade replaced the more commonplace Frag Grenades employed by the Space Marines for advanced variants which contained toxin-impregnated crystalline splinters that have been darkly claimed to be based on xenos technology.
  • Master-crafted Plasma Blaster
  • The Sarrisanata - The Sarrisanata, or Pale Spear, was one of a number of strange and esoteric weapons associated with the Primarch of the XXth Legion and rumoured to be a strange xenos artefact whose forging predated even the rise of the Eldar. This double-bladed spear flickered seemingly out of phase with the material universe when wielded, emitting an eerie and otherworldly howling, and was able to pierce any physical defence it encountered without impediment, ripping them apart at a molecular level. Against living matter, it inflicted hideously gaping bloodless wounds as the flesh where it struck dissolved into oily smoke.
  • Nuncio-Vox
  • Cognis Signum
  • Cameleoline Cloak


  • Codex: Space Marines (5th Edition), pp. 42-43
  • Codex: Chaos Space Marines (4th Edition), pp. 20-21
  • Codex: Chaos Space Marines (3rd Edition, Revised Codex), pg. 40
  • Codex: Chaos Space Marines (3rd Edition, 1st Codex), pg. 32
  • Codex: Chaos (2nd Edition), pp. 14-15
  • Deathwatch: First Founding (RPG), pg. 78
  • Imperial Armour Volume Five - The Siege of Vraks - Part One
  • Inquisitor: Core Rulebook (RPG)
  • Index Astartes IV, "The Enemy Within - The Alpha Legion Space Marine Legion"
  • Realm of Chaos: Slaves to Darkness
  • The Horus Heresy - Book Three: Extermination (Imperial Armour), pp. 82, 85-86, 264-265
  • White Dwarf 310 (US), "Battle Report: The Defense of Cephian IV", pp. 94-113
  • White Dwarf 277 (US), "Index Astartes: Alpha Legion"
  • Legion (Novel) by Dan Abnett
  • Fulgrim (Novel) by Graham McNeill
  • Deliverance Lost (Novel) by Gav Thorpe
  • The First Heretic (Novel) by Aaron Dembski-Bowden
  • Age of Darkness (Anthology), "The Face of Treachery" by Gav Thorpe
  • The Primarchs (Anthology), "The Serpent Beneath" by Rob Sanders
  • The Seventh Serpent (Novella) by Graham McNeill
  • Praetorian of Dorn (Novel) by John French
  • Legion of the Damned (Novel) by Rob Sanders
  • Warhammer 40,000: Dawn of War
  • Warhammer 40,000: Dawn of War - Soulstorm


Horus Leman Russ Lost Primarchs Ferrus Manus Fulgrim Vulkan Rogal Dorn Roboute Guilliman Magnus the Red Sanguinius Lion El'Jonson Perturabo Mortarion Lorgar Jaghatai Khan Konrad Curze Angron Corvus CoraxAlpharius Omegon

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