The Osirian Psybrids was the name given by the Imperium to a species of powerful xenos psykers that the Space Marine Legions faced during the campaigns of the Great Crusade in the late 30th Millennium.
Clad in baroque armour containing ghastly, barely-corporeal forms of mist, the Psybrids psychically travelled across the galaxy in hourglass-shaped voidships and used their immense psychic strength to mentally enslave other intelligent species to their will, such as Humans and Orks.
Psybrids were first encountered by the Ultramarines Legion before their reunification with their primarch Roboute Guilliman during a campaign to suppress a revolt against Imperial rule known as the Osiris Cluster Rebellion, which sought to reclaim the Osiris Cluster of eleven formerly Compliant worlds. That campaign led to the death of Lord Commander Gren Vosotho, the first Legion Master of the XIII Legion, and resulted in a defeat that nearly crippled the XIII Legion's morale going forward.
After the Ultramarines were taken over by Guilliman, he recognised the wound this terrible defeat had left in the minds of his Space Marines and he deliberately sought out the xenos for a second confrontation. When this came, at the Battle of the Eurydice Terminal, this time the Ultramarines, guided by the wise hand of their primarch, destroyed the Psybrids utterly, putting an end to their scourge upon the galaxy and eliminating the only true stain to his gene-sons' honour as a Legion.
History[]
Osiris Cluster Rebellion[]
By the year 833.M30 early in the Great Crusade, the XIII Legion had increased in number to an active force of around 33,000 Space Marines, whose primary battlegroup now consisted of the autonomous 12th Expeditionary Fleet. This expansion of their number in a relatively short space of time had been due to two principal factors.
The first was that their particular practical style of warfare had a tendency to avoid casualties where possible compared to the tactics employed by certain other Legions. The XIII Legion avoided battles of attrition and prided themselves on achieving strategic goals with the minimum expenditure of life -- and where salvageable Human worlds were involved, this desire was also extended to the minimisation of civilian collateral damage.
The second was a latterly revealed aspect of their gene-seed. While the rates of gene-seed implantation success for the XIII Legion's zygote type were very close to the median level, it had proved to be in the highest resistance band to errors during extensive replication -- a meridian matched only by the I Legion's own core sample -- suffering relatively little mutation or deviation in the subsequent generation of harvested Astartes organs. This allowed the Legion to steadily expand its numbers, even without the genetic stabilisation brought by the availability of a primarch's own mature gene-code.
At this time, the Emperor, in command of the might of the Principia Imperialis expeditionary fleet, Ferrus Manus and his X Legion and Horus and his Luna Wolves, respectively, led the three main thrusts of the Great Crusade. They were pushing on into the outer void far beyond the Segmentum Solar.
But such was the size, self-sufficiency and genetic stability of the XIII Legion that the 12th Expeditionary Fleet alone was entrusted with the task of exploring the extent of the inner galactic disc and its densely packed star systems coreward of Terra. This was why when a secession crisis unexpectedly flared up close to the capitoline systems of the Segmentum Solar itself, the XIII Legion was the closest available Legion and the swiftest to respond.
The Osiris Cluster, a grouping of eleven star systems making up the inner portion of the Segmentum Solar's second quadrant, had suddenly and without warning declared secession from the Imperium. Chartist merchant vessels had been seized, Imperialis Armada naval patrol squadrons fired upon and driven off by system defence ships, and agents of Imperial authority rendered silent and assumed dead.
The Human-inhabited worlds of the Osiris Cluster, many technologically advanced at contact, had originally come into Compliance during the Great Crusade's eighth standard year in relatively bloodless order. It had been viewed as a highly successful campaign in which the XIII Legion itself had a hand. That the Osiris Cluster had now fallen into open rebellion was deemed an affront to the Legion's honour by its Lord Commander, Gren Vosotho, and the Legion Master of the XIII Legion had vowed to bring the matter to a resolution as swiftly and emphatically as possible.
Vosotho, acting on initial intelligence reports, ordered the warships of the 12th Expeditionary Fleet to proceed directly to the halo world of Septus XII, leaving behind the fleet's support elements, lumbering troop transports and forge ships guarded by its slower combat vessels. The target of this rapid strike force was to be the atmospherically-sealed city of Cabasset, located on the night-side of Septus XII, and the economic and political capital of the Osiris Cluster.
A strike there before the rebels had time to consolidate their forces, Vosotho reasoned, might end the rebellion in a single, bloody stroke. Breaking into realspace in the outer system, the power of the 12th Expeditionary Fleet's two score of capital warships, led by the Legion's flagship, the Goliath-class macro-battleship Sethaln's Thunder, easily swept aside the system defence monitors and fireships sent out to intercept them. Immediately after the short firefight, in which the Space Marine ships sustained no losses, they engaged in a brief and equally successful long-range precision bombardment to defang Septus XIII's orbital defences, before moving to attack the planet itself.
Vosotho had formulated a plan of attack based around a decapitation assault against the governmental and environmental control complexes on which all life in the hive city of Cabasset was dependent for survival. The strategy was a variation of a tried and proven tactic in part developed from close observation of the Luna Wolves' mastery of such attack forms, and which promised a quick resolution with the minimum of damage to the Hive World's infrastructure and an object lesson in the futility of rebellion against the rule of the Emperor.
The plan itself was predicated on detailed prior knowledge of the world as an Imperial holding and a military assessment of the potential numbers and capabilities of the rebellious militia forces the Legion was projected to encounter. Unfortunately, every assumption Vosotho and his command staff had made about what awaited the Legion was wrong.
Attack on Septus XII[]
The attack began well enough, with the close support fire of the Sethaln's Thunder opening up great rents in Hive Cabasset's protective outer shell into which Vosotho personally led his Legion's Stormbirds to the attack.
Resistance was immediately far heavier than expected as the landing force became swiftly bogged down in Human waves made up of at first hundreds and soon thousands of dead-eyed civilians crudely stitched into makeshift pressure suits and armed with improvised weapons of every sort, not least among them explosive mining charges converted to suicide devices. The XIII Legion quickly modified their tactics to inflict maximum attrition but, heedless of casualties, the tide of bodies pressed on in cold silence and it was quickly apparent that this was no mere rebellion and no ordinary enemy.
Unwilling to allow his attack to be stalled and his invasion force surrounded, Vosotho called down reinforcements and ordered his attacking squads to press on, relying on speed and coordination, as well as the superiority of his Space Marines in close quarters combat, to carry the battle.
Slowly and with steadily growing losses, the Legiones Astartes forced their way deeper into the hive city and one by one began to claim their tactical objectives, crushing better-armed but equally vacant-minded opposition formed of what had once clearly been the bodyguard cadres of the hive city's nobility. But once the XIII Legion was heavily committed and kilometres deep into the hive the trap was sprung.
A xenos fleet of unknown type and origin, comprising five vast hourglass-shaped vessels whose structures turned and rotated ceaselessly like clockworks, appeared with great speed from within the fiery corona of Septus' giant star. Realising the disaster that was about to unfold, Vosotho called a general retreat from the surface, but as his forces battled to return to their gunships and transports, the assault on the Space Marines intensified as the nature of the attacks began to change.
While the waiting Stormbirds fell under concerted all-out attack in an attempt to cripple or destroy them, fresh mobs of grasping civilians poured from side-junctures and corridors, their intention not to kill but to overwhelm and pinion individual Legiones Astartes, drowning them in their mass of bodies, heedless of the cost of life. Above them in the void, the two fleets clashed.
The great hourglass craft, each easily out-massing the gargantuan Sethaln's Thunder, lashed out with blazing whips of elemental particles, scorching and burning the Imperial warships and engulfing any fighter squadrons or torpedo salvos that came close in collapsing gravitational singularities, annihilating them utterly.
The 12th Expeditionary Fleet was overmatched but fought on valiantly, causing one of the titanic xenos craft to fall back, strangely-coloured vapours bleeding luminously from its rent hull, but at the cost of a dozen of its own number, while the Sethaln's Thunder, at that point a burning wreck, tumbled out of control through the line of battle. It was then that fearful figures, aglow from within with sickly light, began to materialise among the attackers both on the surface and directly onto the warring Imperial vessels.
Armoured in some form of baroque bio-mechanical containment suits, the creatures within were barely corporal; ghoulish shapes of glowing mists whose gauntlets spat ethereal fire and whose alien wills reached out to crush the minds of those who resisted them. Vosotho's final command was for the fleet to withdraw with as many of the XIII Legion as could be recovered, but withdraw it must. A new enemy of the Imperium had been met, and word of it must reach Terra at any cost.
Vosotho committed his life to the command of the rearguard on the surface, as penance for his error, and his last act was to transfer Legion command to the most senior surviving commander present in orbit, First Master Marius Gage. It was a testament to Gage's swift thinking and tactical acumen that he was able to hold off the enemy vessels until every surviving Stormbird from the ground assault had departed the planet, fighting a swirling three-dimensional battle of thrust, counter-thrust and retreat which held the enemy titan-ships at bay until the 12th Expeditionary Fleet had fought its way clear.
Ultimately, what could have been a disaster had been fought into a mere defeat, and when all was afterwards measured, the XIII Legion had suffered a little over 6,500 Space Marines lost, the largest tally of any single battle in the Legion's history. Although this was approximately a fifth of its fighting strength in terms of Astartes, the lost counted among them much of the elite of the Legion, many of them Terran veterans from its founding and its Lord Commander Gren Vosotho with them.
Its fleet had also suffered heavily, with a quarter of its warships lost or irrevocably damaged, not least of all its flagship. Just as bitter a blow was to the Legion's pride and honour at the defeat to which their overconfidence had led them. They hungered for vengeance but even this was denied them.
When the XIII Legion returned to the now-quarantined and blockaded Osirin Cluster a little under a standard year later , it was with a force heavily augmented from the Solar Armada, elements of the XVIII Legion (Salamanders) and specialist anti-psyker cadres from Terra. Of the enemy xenoforms the Officio Biologis had designated "Osiran Psybrid," there was no sign. Instead, the Imperials found worlds either left as wastelands of the unburied dead or locked in turmoil and civil strife.
Piecing together fragmentary records from planetary dataspheres and Human minds alike all but purged clean, it was impossible to know from where the xenos had come or where they had gone, only that they had operated covertly at first, insidiously claiming worlds outright; burning out the wills of their populations, stealing away some bodily into the void, and leaving the others to simply mindlessly perish by starvation or inaction in their absence.
Other worlds they had sent first into rebellion and then strife through covert psychic domination of their rulers and manipulation of their population's fears. The revelation was of a foe perhaps not numerous, but both insidious and frighteningly powerful, a clear threat now marked for extermination by the Emperor's own writ.
In the wake of the short campaign, empty of glory, which brought the remains of the Osiris Cluster back into the Imperium's control for repopulation, the XIII Legion swore a blood oath of vengeance against the xenos wherever and whenever they might appear again. The Legion, now under Marius Gage's stewardship as the new Lord Commander and Legion Master, reorganised and sought to quickly replenish its numbers and supplies, and afterwards redoubled its effort in the Great Crusade's service, as if trying with each fresh victory to prove that the defeat at Septus XII had been an aberration never to be repeated, and the name of its lost master and indeed the battle in which he fell became a thing no longer spoken of but which dwelled as a shadow at their shoulders.
There existed within the Legion now a brooding sense of loss and a canker of doubt in its own abilities, and in the hearts of its Legionaries grew the desire, always present but now lent keen impetus, to reunite with their primarch as a balm to all their ills, to become -- as they saw it -- whole. The dark irony was that more than two Terran years previously, unknown and withheld from the Legion's knowledge and before the events at Septus XII, their primarch had been located by the Emperor, but owing to the vagaries of the Warp, contact would not prove possible for several more standard years.
During this period, brief as it was and yet seeming an eternity to the sons of the XIII, the Legion fought on with a relentless but joyless hunger for battle, taking world after world for the Great Crusade in rapid succession, but shunning now both the laurels of victory it once courted and the respect of its peers it once craved, until the hour of its salvation came at last.
Battle of the Eurydice Terminal[]
Since his takeover of the Legion in the fourth solar decade of the Great Crusade after his rediscovery by the Emperor in 837.M30, Roboute Guilliman had succeeded in transforming the XIII Legion into an intricate and highly functioning weapon of war, and in doing so had built upon a track record of success in battle which held very few stains of defeat.
For more than half a standard century the Legion had gone from strength to strength, waging Compliance actions and liberating Human-settled worlds for the Imperium across the eastern reaches of the galaxy, and forging the Realm of Ultramar in the process.
Though not yet having reached the decisive numerical superiority of the other Legions, it would manifest by the time of the Horus Heresy, yet the Ultramarines of 899.M30 were perhaps already on the cusp of becoming the largest Legion, as their ranks, then standing at around approximately 166,000 Legionaries, stood them in the forefront of their peers.
The Dark Angels, who in the previous decade to this had been undoubtedly the most powerful single Legion, had fallen in number and evened this figure, having suffered massive casualties holding the line during the famed Third Rangdan Xenocide. 50,000 Space Marines had spent their blood in preventing the destruction of perhaps the entire northern Imperium by the alien menace from the outer darkness.
The Ultramarines in contrast had spent solar decades in building up their forces and expanding the frontiers in the galaxy's east, having had the advantage of their excellent network of supply and recruitment, and their primarch's formidable generalship was at a zenith of its strength thus far. Yet for all this, Roboute Guilliman knew that a shadow of doubt afflicted his Legion's soul. That doubt had its origins in its darkly storied defeat in the Osiris Cluster Rebellion a few short Terran years before the primarch's reunion with his Legion.
Marius Gage's tenure in command as Legion Master had commenced with this disaster, and it became a baleful influence in the psyche of the Legion, a thing which while left unspoken nevertheless had power, and that even seemed to cast a pall over the Legion's recruits unborn when the battle was lost. The primarch knew that the only way to purge his Legion of this shadow of the mind was to find once more the xenos known as the Osirian Psybrids, and with the Ultramarines at his back, destroy them utterly.
To this end, ever since he had first reviewed reports of the action when he took over his Legion, Roboute Guilliman had begun planning the Psybrids' destruction, analysing and re-analysing every facet of the Legion's battle-logs, gun-picter footage and even the deep auspex data gathered from the aetheric cogitators of the warships that had survived for microscopic fluctuations.
In the solar decades as his Legion had gone from Compliance to Compliance, war zone to war zone, the primarch had never stopped running continued theoretical battle scenarios against the macabre and powerful xenos, knowing that one day they would make their reappearance and that he and his Legion would be waiting. But solar decades passed and they did not return.
There had been rumours of course, unsubstantiated accounts passed on from frontier Rogue Traders, intermittent reports of inexplicable massacres and mass disappearances, but the galaxy, even within the fold of the growing Imperium, was a strange and dangerous place, and the evidence was seldom conclusive as to the culprit, or pointed to the more commonplace but no less deadly privations of several known xenos species.
Only at Maxilla Veritas near the Maelstrom, twenty-six standard years after the Osiris Rebellion, was the evidence for the Psybrids involvement considered viable. But by the time fast cruisers from the Ultramarines fleet arrived, the trail was already long cold and the planet's death bore silent witness to the Psybrids' passing. It was in the closing segments of 899.M30 that conclusive word finally reached the Ultramarines primarch that the Psybrids had not only been encountered, but met in battle.
Relayed from the central astrotelepathic chamber of Terra, the strange report had come from a sub-fleet of the XII Legion, then in its last days as the War Hounds before its own primarch, Angron, was found. The fleet, under the command of Praetor Erad Krüg, was fighting on the southwestern extreme of the Great Crusade's frontier near Eurydice Terminal. Here the War Hounds had been engaged in repelling an attack on the frontier outpost world by Ork void raiders from the self-styled Glortian Empire from the untracked abysses beyond.
The War Hounds, though severely outnumbered, had held off the repeated Ork attacks through a series of savage voidship boarding actions in close orbit and high intensity assaults on their landing zones, preventing the xenos from gaining a foothold on the ground. It had been during the latest of these assaults, the largest yet attempted by the Orks, that a mysterious third party had attacked both sides.
When the Ultramarines retribution fleet arrived, not even the superhuman intellect of the Ultramarines primarch could have predicted what his Legion would find there. The entire system had been sundered into a battleground littered with burning debris and the radioactive echo of heavy weapons fire. The Ultramarines found the last surviving few hundred Legionaries of the XII Legion, the remnants of a force that had once been ten times its number, led by the terribly wounded but still commanding Erad Krüg.
The War Hounds praetor detailed to Guilliman the story of a strange and terrible battle in which the Psybrids had managed through their mental powers to enslave a vast feral population of Orks to do battle for them against their own kind, and had sought to do the same to the Imperial defenders of Eurydice. Only the War Hounds had proved able to resist the creatures' baleful influence, but massively outnumbered they had paid for their resistance in blood, and would have been overwhelmed regardless if huge numbers of enraged Orks, seemingly the massed forces of the entire Greenskin Glortian Empire, had not swarmed into the system.
During the ensuing battle, the Orks fought with unbelievable fury even given their warlike species' tendencies, compelled by their baleful masters to exterminate their enemies. More of the gargantuan Psybrid hourglass voidships in turn had appeared to reinforce their fellows, and with them thousands of enslaved xenos warriors and ships, few of which were known even to the lexicanic data cores of the Imperial warships.
Eurydice Terminal had become a killing star; a vortex of destruction that was even now calling more armies to their deaths, and here the Ultramarines had come to restart the battle afresh. Guilliman, having apprised himself of the tactical situation, modified his battle plans accordingly and without pause put his strategy of attack into operation.
Despite Erad Krüg's request for his surviving Legionaries to be lifted from their wrecked vessel and given a place in the line of battle, the War Hounds were denied; this would be a battle for the Ultramarines alone. It was to be a tactical operation more traditionally the specialty of other Space Marine Legions than the Ultramarines, but at which Guilliman's own warriors were still well-versed -- a full assault-strike voidship boarding assault.
The primarch's plan of attack was a shockingly direct one. His fleet didn't pause for a long-range bombardment or present a broadside and pound the enemy at close quarters; instead, he ordered his Legion to conduct a full boarding strike without prelude. Guilliman drove the core of his fleet and with it nearly 100,000 Ultramarines into the heart of the enemy.
It was not without irony that Roboute Guilliman records in his own testimony about the assault that he and his Legion were adverse to strategies which resulted in a heavy cost of Ultramarines' lives; this single action would dispel that myth and illustrate the truth that such tactics were often wasteful and unneeded by a skilled general, but when such sacrifice was the most efficient and indeed perhaps the only path to victory, he and his Legion would pay that price with fervour and unbreakable determination.
The Ultramarines at last unleashed their wrath as they closed with the enemy vessels, hundreds of gunships and assault rams roaring from their flight bays to the attack as the Ultramarines fleet unleashed a cannonade of a thousand lance batteries and macrocannons. The Psybrid nomad-vessels lashed about them with frenzied whips of elemental energy, and all around them hulls burst and ships burned, but it was too little against the unstoppable tide of ire which crashed against them.
Through the maze-like networks of turning corridors like the innards of a great machine, the Ultramarines stormed with deadly intent, destroying as they went. Soon they encountered ghoulish, half-solid vapour forms, lean and gaunt without their exo-armour, who fought with the savagery of caged animals, burning bright with psychokinetic energy and striking out with mind-burning blasts of power, but for every Legionary who fell, a dozen pressed forward in their place and, one by one, the Psybrids began to be corralled, cornered and killed.
Led by axe-and-shield-wielding Invictarii and moving bulwarks of Terminator Armour-clad Veterans, the Ultramarines pressed into the heart of the great vessels, mining the corridors and power junctions with Melta Bombs and atomantic implosion charges as they went. For the warriors of the XIII Legion were implacable, and in them had been woken a rarely displayed drive for vengeance against the Psybrids that could not be diverted nor denied.
It was Roboute Guilliman himself who breached the innermost chamber of the largest of the hourglass ships to find the master of the Psybrids. It was a towering, multi-limbed gestalt-thing, thrice the primarch's own height, whose long, almost equine head screamed out shockwaves of ceramite-breaking force as its inner sanctum was invaded. But even as his own Terminator-armoured honour guard staggered and fell under the psychokinetic onslaught, the primarch, with his Chief Battle Psyker Aaroth Ptolemy beside him, charged.
The Psybrid-king reared up above them, its clawed arms bearing strange weapons like the image of some forgotten devil-god of Old Night, but Guilliman with the strength and speed born of the Emperor's unmatched arts struck, cleaving the creature limb from vaporous limb as Ptolemy fought it on the psychic plane with every ounce of power in his possession, sacrificing his life so that Guilliman would be defended from the nightmarishly powerful creature's psychic assault.
The monster finally fell and the primarch of the Ultramarines enacted his Legion's vengeance, ripping the thing's glowing brain from its skull and crushing it under his heel. One by one the towering hourglass vessels of the Osirian Psybrids fell, either torn apart by explosive charges from within, or rent to flinders in the crossfire of the waiting Ultramarines' echelons as they tried to break free. There was no escape.
As the Psybrids died, so too did their slave armies still warring on the ground, and soon only the Glortian Orks, already mauled and all but exhausted, remained, and the Ultramarines made short work of driving them away once more into the outer darkness.
The blood price of the battle had been high enough, several thousand Legionary casualties, and many among them veterans of his Legion's Terran roots, eager to be the first in battle in order to expunge the failing of the past. But it had been a price willingly paid for vengeance, and it would be a price and more that the Ultramarines Legion would willingly pay again in the future.
Sources[]
- The Horus Heresy Book Five: Tempest (Forge World Series) by Alan Bligh, pp. 96–99