The Xana Incursion was a desperate covert campaign conducted by a Legiones Astartes Blackshield irregular force as well as a small force of Dark Angels against the recalcitrant Forge World of Xana II in 009.M31, during the galactic civil war known as the Horus Heresy.
Intelligence had reached Terra that the Renegade Forge World on the western fringe of the Imperium had reached an accord with the Traitor forces to supply the Warmaster Horus' armies with vast output of arms and materiel. The bargain was to be sealed with the delivery by Xana II of a number of newly created powerful Ordinatus class weapons undergoing final field tests.
In what was effectively a suicide mission, a handpicked force of Legiones Astartes, including many Blackshields -- in this case Space Marines who had chosen to remain loyal despite their parent Legion's treachery -- was despatched under great secrecy to destroy the war machines and drive a wedge between Xana and the Traitors. Two Ordinatus were captured by the Loyalist force and evacuated from the surface of Xana-Tisiphone, to be maintained and utilised by Loyalist tech-magi in latter campaigns of the Heresy.
Much of what is known to the record about the incident known as the Xana Incursion is a dossier assembled from diverse and incomplete secondary sources. These include the akashic archives of the Amphion recovered from her hulk after the Battle of Triton, the harvested data-looms of the Xanan exile-savant Mordifia Turul and the apocryphal appendix to the Tears of the Gorgon, an allegorical and now-prohibited treatise associated with the (redacted) Chapter of the 3rd Founding. The primary source file of the operation, held within the Seal and Office of the Sigillite and the Divisio Sicarii, was lost during the devastation of the Siege of Terra. It is also certain that during the Wars of the Heresy, the operation was itself kept secret by the orders of the Sigillite even from Imperial High Command. As such, while there is good evidence to suggest that the real Traitor embassy had been somehow compromised, intercepted and replaced by covert Imperial forces that cannot be contested, it is also highly likely that the individual masquerading as Raxhal Koraddon was in fact Endryd Haar, an outcast not of the Sons of Horus but the World Eaters Legion, who remained loyal, but the provenance of at least 1,000 Legiones Astartes accompanying him remains a matter for some conjecture.
It is the general consensus that this force, undertaking what was in effect a suicide mission with little hope of recovery or rescue even if success was achieved, was made up of veteran Legiones Astartes who, like Endryd Haar, had remained loyal, even though their parent Legions had turned Traitor. This desperate and damned force had little to lose, it can be argued, and nothing to gain save redemption in death. Just how Endryd Haar survived, and survive he did as his actions during the later Solar Wars are a matter of record, also remains unknown. Of equal enigma is the depth of the Dark Angels' involvement, but perhaps the most unknowable and disquieting mystery regarding the Xana Incursion is the horror which erupted on Xana II after the Archmagos and the attack of the Dark Sovereign.
By the closing divisions of 009.M31, the bargain between Xana and the Warmaster's proxies was in its final stages of conclusion. It was, in the ancient manner, to be sealed with an exchange of gifts. Though the transfer of billions of tonnes of arms and armour would be part of Xana's fealty to Horus, these first gifts the Vodian Consistory would present would be unique and incomparable. They would be worthy of one who meant to be master of the galaxy entire; Xana would gift Horus with the power of Ordinatus.
The Ordinatus classification held the most powerful and arcane mobile weapons platforms in the Mechanicum's arsenal. Much like the Titans whose firepower they often outstripped, the Ordinatus varied in scale and potency: from the truly colossal, unique and unreplicable relics of the Dark Age of Technology, the Ordinatus Primaris, such as the Mars and Endymion whose power was legendary, even compared to the god machines of the great Legio Titanicus, to the lesser but still gargantuan and deadly Ordinatus Minoris sub-classes. The Minoris were, at the height of the Great Crusade, within the reach of only the most potent Forge Worlds to construct, and even then only in the most limited numbers. Such were the gifts that Xana offered; no less than three such terrifying weapons of the Ordinatus Ulator pattern, fully battle-ready and armed with devastating sonic destructor weapons. These were Titan-killers, slaughterers of armies, each powerful enough to turn the tide of a battle at a stroke, far beyond any super-heavy tank in potency and dwarfing the firepower of even the mighty Diamatine siege-guns that had fallen into the grasp of the Iron Warriors earlier in the Horus Heresy.
These Ordinatus, named Mithrax, Nepothax and Ashurax after Ancient Terran deities long-dead of worship, were first to be demonstrated before the Warmaster's chosen emissary at the Forge World's own proving grounds on the moon of Xana-Tisiphone; afterwards, their ceremonial handover would act as a symbolic sealing of Xana's loyalty to Horus. That this trio of mighty weapons would be given over to Horus himself to dispose of as he saw fit was both a potent asset to gift the Warmaster with, and also it might be seen as a coded barb thrust in the side of the Traitor Mechanicum Fabricator-General Kelbor Hal, who though he sat high in Horus' cause, but had never himself made such a direct gift, keeping those few Ordinatus he and his satraps had at their disposal firmly under Mechanicum control. By this act Xana's lords sought perhaps to set the groundwork to become Mars' rivals in the Traitors' cause, not simply a subordinate Mechanicum force.
Emissary of the Uncrowned King
The hand of the Warmaster in the final matter of the alliance with Xana was to be no priest of Davin alone, but one of his own warlords, one of his own blood; Raxhal Koraddon -- a chieftain of the Reavers raised to captaincy for his bloody endeavours during the scouring of the Sons of Horus Legion of its Loyalists on the ash-strewn ruins of Istvaan III.
Koraddon had in the years of war that followed Istvaan III gained a fierce reputation, first during the Dropsite Massacre and later in leading a score of Dark Compliance actions for his Primarch across the northern reaches of the Segmentum Obscurus. Koraddon's ruthless and prideful reputation preceded him, as did knowledge that he was looked upon with favour by Horus, making him an honoured, if threatening choice to serve as the Warmaster's emissary in the matter. The vessel which bore him to the Xana System was no less a display of power; the Geryon-class Grand Cruiser Cicatrice Tyrannis, taken as a prize by the Traitors during the Battle of Port Maw earlier in the war, her once white and golden hull now scorched black and pitted by the fires of untold void battles since her fall from grace. With the Cicatrice came an escorting squadron of eight frigates of various types and four Isos-class fleet tenders. These latter vessels were small, armed, warp-capable transport ships designed to ferry vital supplies to warships in frontline service, but who bore now a far stranger and more macabre cargo; the Warmaster's gift to the Lords of Xana. Carried within these ships were hundreds of locked and armoured cargo pods, within which travelled the wreckage of Istvaan, of Momed and of Autosarat, and other unknown battlefields where the Sons of Horus had met their brother Legiones Astartes in blood and triumphed. The legacy of the dead was to be the Warmaster's gift to Xana.
Sealed in these containers were the fallen of those Legions the Sons of Horus had fought, and along with them a ruin of broken tanks and sundered war machines, shattered arms and rent armour -- the charnel remains of a dozen Loyalist Legions. This was a carrion feast of technology and gene-craft priceless to the Lords of Xana; to them it was no mere detritus of battle, but a treasure store of lore and techno-arcana for those with the skill to decipher its secrets and who cared nothing for the writ of Mars, nor what the Emperor had forbidden them to study.
Even as the Cicatrice Tyrannis and her escorts entered close orbit of the immense gas giant Xana I on final approach to the Forge World itself, the auspex grid of the outer planetary system came alive with emergency signals and alarms. Perilously close to the gravity-shadow of the system's inner sphere, realspace ripped open and the brute and barbed shapes of scores of warships forced their way out of the Warp. The tracking augers and void-cogitators of Xana's sleepless defensive engine-minds swept the intruders, quickly analysed the fleet, and came to the absolute conclusions of hostility, swinging into baleful wakefulness. No fewer than five capital class vessels were identified, Imperial in origin and Loyalist in allegiance, with no effort made to hide who or what they were. At their head was a vessel immediately identified as the Amphion, one of the mighty Gloriana-class Battleships and an example of the type which often provided the flagships of the Legiones Astartes themselves, outfitted as a pure device of void-born firepower, and one of the lynch pins of the Solar fleet itself. With these capital ships came a slew of smaller escort craft and a dozen transport craft whose anomalously over-powered emissions marked them as one thing only to the cold intellect of the machine-spirits; fire ships, loaded with warheads and volatiles designed to inflict catastrophic damage in suicide attacks against their targets. Machine-spirits conferred with magos, and with blinding speed beyond human comprehension was data analysed, checked and re-analysed, conclusions drawn and tested, re-submitted and issued as directive. This then was Dorn's judgement come at last, or at least part of it, the make-up and composition of the powerful fleet indicated a raid-in-force, not an invasion, with its target the waiting fleet of loaded macro-conveyers, protected within Xana I's debris rings. Terra had decided that if they were not to have the bounty of Xana's forges for themselves, then none would, and calculated that the risk of deploying several potent heavy units from Terra's own defence armada was worth the reward this mission of destruction entailed.
With faultless precession, the defenders of Xana rose to meet their aggressors; squadrons of frigate-sized machine sapient hunter-killers and scores of autonomous weapons platforms rose from within the vaporous depths of Xana I's atmosphere to protect their master's wealth and spat their payloads with synchronised fury, sending hundreds of void torpedoes hurling towards their target, the plasma drives of the shark-like hunter-killers blazing in their wake. From their own stations on allotted patrol routes across the planetary systems, Xana's own interstellar warships, battle-arks and attack carriers in the main, far larger than the local defensive vessels, awoke and burned at maximum thrust to intercept the Loyalist assault force, the attack of which, despite the bravery and skill of its Navigators who had dropped the force into realspace close enough to be hours rather than days distant from their intended target, could still be contested before it reached its goal, or at the least a lethal trap would close behind the intruders. Calculations were checked and tactical projections run and re-run thousands of times in bare seconds, secondary waves of munitions roared forth from the surface of the Forge World of Xana II itself and its own sentinel void-battle servitors -- mechanical Kraken the size of strike cruiser -- broke from their steel shells like hollow moons and powered towards the fray. As the white blood cells of a human body swarm and overwhelm an invading virus, so would the war machines of Xana swarm and overwhelm this unexpected attack, no matter its power.
The False War
The news of the attack on the Xana System had inevitably reached the Sons of Horus, whose own vessel had detected the incursion from the Warp of the Imperial forces and bore witness to the apocalyptic response from Xana's defences. Koraddon demanded answers. He was met with profuse apologies for any alarm caused, and assured that the matter would be dealt with promptly and without risk to the Warmaster's delegation, and that there would be no need to alter the planned exchange of gifts and demonstration of the Ordinatus. For Xana, both the demonstration and the impending void battle had become a necessary display of strength before their future allies in ways they had never planned, but no less vital because of this. The Vodian Consistory would not lose face before Horus.
So it was that even as the Loyalist and Mechanicum warships and torpedoes hurtled at unimaginable speeds towards each other in the void far beyond, the matter of Xana's formal alliance with the Traitor cause proceeded with much ceremony and clockwork precision. By prior arrangement the Warmaster's cargo was delivered from orbit, even as Xana II's planetary interceptor batteries fired, cycled and fired again, sending torpedoes speeding into the night on columns of fire. The gift-cargo was landed between the barrage launches, still sealed in consignment to the landing ports of several of Xana's major forge-fanes: Tephra, Escorial and Setna, no doubt to prevent discord in the Consistory itself by dividing the spoils between the archmagos, to be released by code key transfer as the accord was formally made.
Meanwhile, the Sons of Horus warship, Cicatrice Tyrannis, was permitted into close orbit of the moon of Xana-Tisiphone, sheltered from the waves of fire unleashed from the Forge World itself, and Koraddon, with Unvacar Noon at his side, descended with a full company-sized honour guard of Sons of Horus to the surface via wings of fully armed Stormbirds and assault landers; a display of force and perhaps of displeasure that could not be lost on the waiting Mechanicum delegation. Ready to meet Koraddon's party on the edge of the great proving grounds, a vast artificial battlefield outside the half-kilometre high walls of the great prison-forge of Tisiphone-Shaol, was Archmagos-Procurator Gilim Raijan, the prime arbiter of Xana's ruling Vodian Consistory and his personal covenant of magos, guardian-servitors and lexmechanics.
Such records that remain of this meeting are fragmentary and uncorroborated, and suggest a cold and tension-laden encounter between the barely contained arrogance of the Sons of Horus warlord and the chill, precise civility of the Archmagos of Xana, with the strange and macabre figure of the Davinite priest acting as intermediary. Of the impending void battle nothing was mentioned, and after the initial diplomacy and greetings were concluded, the nature of the planned demonstration was detailed.
What was presented to the Warmaster's emissaries was to be a false war of sorts, but one in which the carnage would be very real. Thousands of armed slaves and human chattel, some were abhumans, others forge serfs and adsecularis, while others were military prisoners taken in raids by the Xanites -- soldiers from the Loyalist cause for the main -- were unleashed onto the kilometres-wide proving grounds. Controlled by remote-detonated suicide-collars and spurred on by auto-injected chemicals where needed, this damned regiment was equipped with a panoply of weapons ranging from small arms up to and including even heavy tanks of Imperial pattern, and they had been given a simple but impossible task -- to survive what was coming.
From within the armoured observation cupola of a hulking Mechanicum land crawler, flanked by a pair of Sons of Horus Mastodon carriers forming escort, would the Warmaster's emissaries and the Archmagos Raijan observe the bloody game that was to follow, inviolate behind their void shields but within the thick of the contrived battle. It was to be a thing of sheer destructive spectacle -- a massacre made to order. The vast black vaulted gates of the prison-forge opened and the three monsters emerged into view, Mithrax, Nepothax and Ashurax, each Ordinatus fully armed and operational, and each with a coterie of Sons of Horus Techmarines on board to observe their operation first hand. With a coded signal which promised instant death if compliance was not given, the first wave of enslaved soldiers attacked, hundreds and then thousands of infantrymen pouring across the broken, shell-pitted ground. In response, the Ordinatus spread out and deployed, advancing, forming an echelon, half-seen clusters of humming automata hovering to guard each huge war engine's flanks should anything close to endanger their mighty charges.
Like a vast ground-swarm of insects, the infantry wave surged and began to encircle the rumbling metal beasts, the Ulators' vast and baroque cannon beginning to crackle and glow with building energies of savage force, building until flares of sudden lightning arcs and shimmering surges of distorted air spat from their barrels and coils like angry ghosts. The first of the desperate attackers' weapons fire -- heavy stubber rounds and unguided rockets -- had only just began to patter harmlessly from the Ordinatus' all-encompassing protective power fields when at last the Ulators' sonic destructors spoke. There was a brief, blinding flash. A roaring, all-consuming silence that devoured all sound, the surface of the world itself seemed to ripple like a tortured sea, and in that instant a thousand lives were snuffed out. Bodies, torn to red rags by the all-destroying waves of sonic energy, were blasted across the battlefield as if driven by a hurricane, and beneath them three great trenches now gouged the earth to mark the unleashed blasts. Beside these furrows scores of bloodied men staggered on broken limbs, their senses devoured and minds shattered. Those fortunate to be far enough away saw the fate of their comrades and fled if they were able, or simply collapsed in shock.
The Ordinatus, implacable, rolled on, the observer column behind them in their wake, towards the ultimate goal of a shattered cityscape some nine kilometres distant; a city that had been built and rebuilt many times in the past, only to be destroyed in the testing of Xana's guns. The signal went out and the second wave was ordered in, this time a mixed force of armoured infantry and supporting armour. The attack was even more desperate, the storm that erupted across the Ordinatus' shields more violent, but the outcome was the same: an army wiped out as by the hand of an annihilating god. The signal was issued again, and again and the bloody charade of war continued, now armoured forces alone, now jump troops, now battle-servitors, now a column of super-heavy tanks to test the mighty Ulators' defences to the limit. The killing went on for hours.
The Shadow of the Angel's Wings
While the power of the three gifts was being so emptily and murderously demonstrated on Xana-Tisiphone, in the void the opposing fleets met. Unimaginable forces of destruction were unleashed as beam lances wove traceries of annihilating light across the void, waves of torpedoes slammed into thunderous barrages of counter-fire and atomic explosions rippled like dying stars across the firmament. The Imperium's battleships formed a conical wedge to protect their lethal entourage of fire ships from attack, their escorting frigates and destroyers darting madly around them to intercept any torpedo salvoes or servitor-fighters that broke through the titanic barrages of the Amphion and her sisters, some paying with their lives to carry out their bloody task, interposing their own frail hulls against the fury. Slowly, Xana's fist of iron closed around the Loyalist fleet, and though scores of Mechanicum hunter-killers perished, torn to spiralling fragments by the macro-cannon and plasma cannonades of the Loyalists, and entire war-arks were sliced in half from stem to stern by the Amphion's prodigious giga-scale primary lances, the attacking fleet began to falter and shrink.
One of the Loyalist battleships, the Dequenne's Fury, fell out of formation, a burning hulk, then soon after a second, the venerable Sceptre of Io, spiralled out of control, the beasts of steel gnawing and coiling across her hull like ravenous ghouls, Thallax Covenants and Castellax battle-automata injected like poison into the battleship's veins as the Solar Auxilia armsmen aboard fought desperately for survival to little avail. The Loyalists' defensive shield forced open, its escort screen stripped away, the fire ships themselves began to flare brightly in their death throes. Slowly, and at great cost, the Xanite Mechanicum were winning the battle: the Loyalist fleet would never reach striking distance of the bounty ships hidden in the debris belt.
The weapons platforms in the murky stratosphere of Xana II had fallen silent at last, their munitions spent, as had the ground silos on Xana II, discharged in full. In the void distant, the matter was now being decided by the brutality of a close-range void battle in which they would play no part. So it was that the Mortis-XI defensive station at the heart of the debris belt's defence network began to cycle down its systems to a defensive posture, the Tech-Priest chorus cyber-bonded to its control gyre reaching out with their djinn-sight to the dozens of weapons platforms they controlled, reporting status and correcting positional anomalies in their deployment caused by their now-reduced mass. Suddenly, their auguries screamed with a new hostile contact, a warship impossibly close, not beyond in the void of space, but beneath them in the thick atmosphere of Xana I. The Mortis-XI station died in an eruption of nothingness, vortex torpedoes ripping it out of reality in a squall of disintegrating wreckage. In its place a sable-black ship sliced out of the mirk, long and wicked as a blade, the near-seamless armour of its surface featureless save for a single crimson icon across its low prow, graven in the image of a winged sword.
The sable ship turned almost lazily in an arc towards the dozens of lumbering transports and freighters whose protection within the debris belt of Xana I was worthless now against this wolf among the flock, and she began to kill. Secondary plasma batteries and defensive lasers spat from the spent weapons platforms towards the murderous vessel but they were too little to even give her pause. On Xana II the cold minds which ruled the forge-fanes quickly identified the vessel, for she was a unique killing engine alongside which their own forces had fought many decades before during the Rangdan wars. She was no mere Legiones Astartes strike cruiser, but a lone relic of Old Night, a thing recovered from the permafrosts of Ganymede by the Emperor's own hand. Her name was the Dark Sovereign, and she belonged to the Ist Legion, to the Dark Angels.
The Wrath of the Betrayed
On Xana-Tisiphone, news of the blade in the dark was shock enough to call a sudden halt even to the contrived carnage of the Ordinatus' demonstration. The macro-munitions explosions of the dying transports in the debris field of the Xana I gas giant were potent enough to be clearly visible in the skies overhead. The Warmaster's prizes were dying in flames, and Xana's void ships were simply too far away to prevent it.
On the observation deck of the hulking Mechanicum crawler, Archmagos-Procurator Gilim Raijan turned to Unvacar Noon, perhaps to offer explanation or perhaps to entreat the Sons of Horus' own warship to attack the Dark Angels vessel, only to find Noon's features melting like wax before him. The emissary's arm flashed out, too fast even for the augmented reflexes of the Archmagos to react against, and a gilded barb sunk into his body, a roaring electroshock surge shorting out his power systems and collapsing his personal defensive shield. Raijan fell back away from his attacker as his own guardian-servitors fell on the blurring, shifting, shadow-quick assassin, but behind himself, he found the armoured bulk of Koraddon looming over him as he staggered. The verdigris-armoured warlord reached down to the fallen Archmagos and wordlessly tore off Gilim Raijan's head with his power fist in a shower of sparks and black fluids, and then pulverised his twitching metal body into scrap.
The Hour of Execution
The Lords of Xana had been deceived, and by that deception the Loyalists' bloody stratagem had borne fruit. Some three hours after the initial exchange of fire of the engagement against the Loyalist raiding fleet led by the Amphion, the full forces of the Mechanicum's void defences had been drawn out and committed to the battle, Xana II's long-range munitions had been expended and their warships were now locked in close-quarters fighting with the Terran battlegroup. The Xanite vessels were now simply too far away to defend their home Forge World, or more importantly, protect the huge supply fleet that lay at anchor in the Xana I debris belt, when a new Loyalist attacker, the deadly Dark Sovereign, launched her own devastating surprise assault from within the gas giant of Xana I's atmosphere.
Amid this general chaos, the sudden battle on Xiphon-Tisiphone went all but unnoticed as another lie was revealed, and those who had masqueraded as the Sons of Horus and the emissaries of the Warmaster revealed themselves to be cut from entirely different cloth. Legiones Astartes they were for the main, but they were not Malcador's chosen -- later to be called Knights-Errant -- these were the bitter fall-out of Legions who had turned traitor while they had remained resulted loyal, a decision many had already paid for in blood and sinew in battle against those who they had once called brother. Their leader was Endryd Haar, a World Eater once, and it was he who had passed for the Sons of Horus warlord Koraddon, who it is likely that he himself had earlier slain. He and those with him had by brutal surprise attack taken over command of all three of the Ordinatus Minoris intended as gifts for the Warmaster, and now with malign savagery, turned their dread power on their creators.
First, the escorting guardian-automata had been shot down and crushed by the Sons of Horus-liveried Mastadon heavy tanks that had served as Koraddon's honour guard, before the baleful power of the sonic disruptors of the Ordinatus had swept nearby Xanite armour and support vehicles to oblivion. The anarchy was further accelerated when the Loyalist Techmarines compromised the local djinn command skein by interfacing with the shattered remains of the Archmagos Gilim Raijan to operate the remote release on the collars of the thousands of remaining war slaves who were to be used in the bloody demonstration of the Ordinatus' power. These armed slaves, once free, fled where they could, spreading further the disorder and wild violence that had been unleashed.
The desperate bid to seize the highly prized Ordinatus was only the beginning of the operation on Xana-Tisiphone. The huge warship which had brought the supposedly Traitor delegation to Xana, the Cicatrice Tyrannis, dropped lower into Xana-Tisiphone's orbit, placing the shadow of the moon between her and Xana II, shielding herself from any retribution that was to follow as her crew ignored all requests to attack the Dark Sovereign or otherwise aid the defence against the Loyalists. The Cicatrice Tyrannis then commenced her own company-scale ground assault on Xana-Tisiphone, Stormbirds and Thunderhawk gunships descending as the power of the Ordinatus was turned upon the cyclopean gates of the great prison-forge of Tisiphone-Shaol, sundering them.
The Fury of the Dark Sovereign
In the debris ring that orbited Xana I, a great and violent tempest was being enacted. One after another, the huge freight ships of the supply fleet, heavily laden with munitions and other volatiles, were torn apart by the fury of the Dark Angels warship's attacks or were set burning and left bleeding their disintegrating cargos into space. The macro-transports, some tens of kilometres long -- never intended for war -- had no arms or defences of their own enough to answer such a deadly craft as the Dark Sovereign, while their ungainly bulk would have made escape impossible even if they had not been caught at station by the blade-like predator ship. As the Dark Sovereign reaved her way through the great arc of supply vessels, cannon blazing as she went, she reached the core of the fleet, where the most valuable prize vessels were kept: brazen-hulled Mechanicum barques and stasis-vaulted dromons, now drawn up into a defensive toroid formation. Compared to the dull hulks of the macro freighters, these transports had teeth enough to answer their attacker, and as the Dark Sovereign plunged down amid them like a knife from the dark, the barque's co-ordinated batteries opened fire on their attacker, lancing the void with blazing streams of super-heated plasma and golden beams of coherent energy.
The Dark Sovereign's shields flared as the barrage found her, silhouetting the blade-like ship in a corona of light, but she came on undaunted, for this was a vessel of the Ist Legion and a veteran of centuries of nightmarish war amid the dark stars. Instead of the close pass to bring her weapons to bear with maximum effect, which naval doctrine dictated and the Mechanicum's logis-cogitators had no doubt also predicted, the Dark Sovereign dived into the heart of the defensive formation, her guns suddenly silent, all available power directed to her shields to weather the storm of counter-fire at point-blank range. She passed her first prey at a scant few hundreds of metres and a talon of Kharybdis Assault Claws stabbed out from the Dark Sovereign's flanks to bury themselves in the Xanite barque's hull. The Dark Angels warship rolled as she sped by and more assault claws speared into a second barque, too close and too swift to be intercepted. A squadron of Caestus Assault Rams broke from the Dark Sovereign and peeled off in the wake of the warship's blazing engines to find prey of their own as the Dark Angels ship found her final target, a long, almost crystalline void dromond, designated now the Mu-571, a singular ship which was perhaps once of xenos origin before the Mechanicum had spidered their own steel-grey workings across its white-quartz hull. The Mu-571's own drives burned white hot as it tried to escape imminent collision, but did so in vain, as the armoured belly of the Dark Sovereign smashed the Dromond's spine and flew on, shredding the Mu-571's void shields to nothingness and setting the ship tumbling out of control, as in its heart-chambers reality split open and the black-armoured figures of Dark Angels Terminators manifested in the lightning-crackle aftershock of their teleporter transit.
The Logic of Survival
Deep within the protected forge-fanes of Xana II, city-sized conglomerations of manufactora, vaults and hive-warrens sunk far beneath the planet's surface, the remaining magos of the Vodian Consistory communed with each other in near-frenzied pulses of data, spanning the world's sub-surface networks. With preternatural speed it can be assumed that they gathered all available information about the catastrophe that was unfolding around them; betrayal, assault, mass destruction, a war on multiple fronts in which they had been comprehensively blindsided and led into trap after trap. How they with their vast machine-augmented intelligences had been so outwitted was an impossibility to ponder later, but for now action was required if survival, the primary directive of any Forge World, was to be guaranteed.
In the face of such a shocking turn of events, paranoia now came to dominate their reasoning. Now, faced with the undisprovable possibility that even more attacking forces were on their way to besiege their Forge World, the Vodian Consistory despatched override signals of recall to their remaining war craft engaged in void battle to defend Xana II and rid it of the "Sons of Horus" grand cruiser which lurked in orbit of its moon like a waiting assassin. Withdrawal of the fleet from pitched combat was calculated to be a costly manoeuvre, but all costs would be borne in defence of the Forge World, and even the now-half-burning munitions fleet was abandoned by the cold equations of survival.
All over Xana II, weapons and scanner arrays were pointed skywards, defensive grids and void shields were realigned to defend against orbital attack, while far below, subterranean mag-lev railguns screamed at speeds past tolerance to re-arm the planet's recently spent missile silos from auxiliary stockpiles held deep beneath the world's seas. All of Xana had mobilised to repel an attack from the void, but this was not from where the attack came.
The Vengeance of the Fallen
At the orbital transfer ports of the greatest of Xana's forge-fanes: Tephra, Escorial and Setna, the Warmaster's gifts stood waiting; several hundred cargo containers divided between them, sealed and inert, ranging in size from metre-square STC pattern handling modules of a kind found in their billions across the Imperium, to megaton-capacity armoured void transit carriers intended to survive the rigours of interstellar travel intact. They had been thoroughly scanned by auspexes on their arrival and no sign of life or active power sources had been found within. Furthermore, echo scans had revealed mass and resonance readings, indicating the presence of just what had been promised; the broken bodies of the Legiones Astartes and their machineries of war. With this being the case, true to the diplomatic bargain that had been struck, not a single container had yet been breached or opened. What was to happen next remains a matter of contention by those who have looked back on this incident, and must be reassembled only by fragments of ancillary data, scattered pict-and vox-capture data from seized enemy archives and hearsay well after the fact, the truth perhaps dying with so many other truths in the losses incurred during the Siege of Terra where so much else was also lost. But by all available evidence, the dead walked on Xana II.
Almost as one the cargo containers were broken and blasted open from within, ceramite-clad fists smashing through to grasp the air as if called forth by some unheard summons. Darkly armoured figures came forth in grim and silent advance, bearing the livery of the fallen Loyalists, of the Raven Guard and Salamanders Legions, even of the Imperial Fists and White Scars, but most bore the scorched and rent livery of the Iron Hands, of Clan-companies slaughtered wholesale on the black sands of Istvaan V, and more sinisterly also of Clan-companies that had fallen long before, during the darkest days of the Great Crusade. Of this army of the dead, there was no leader to be discerned, no command signals or command vox transmissions were recorded, only an oscillating electro-spectral field of unknown origin which seemed to pulse relentlessly from tomb-containers from which they came. With them followed scores of Dreadnoughts from the larger cargo units, their shells as damaged and abused as the armour and bodies alongside which they walked, but they were no less functional for it, and behind them rumbled forth half-wrecked tanks and rapier weapons platforms, humming with power and the rattle of loading shells. Those nearby automata and tech-thralls that met this sudden onslaught were overwhelmed in moments and the silent army quickly fanned out, ramshackle and here and there stumbling on broken limbs and reeling as it went, but still with deadly speed and murderous purpose. Soon alarms sounded and the defenders of Xana, their unceasing vigilance set skyward, turned to make swift counter-attack to the invaders in their midst and found themselves facing a foe of singular, suicidal ferocity.
Adsecularis techguard clades and servo-thralls barracked near the starports were the first troops to respond, but quickly proved no match for the grim tide of death pouring from the cargo containers, their bodies broken by unwavering volleys of bolter fire or simply ripped apart in hand-to-hand combat too one-sided to deserve the name. Taghmata Castellax maniples and Tech-Priest-commanded heavy weapons detachments soon reached the fray but found themselves dealing with Legiones Astartes who fought and died with cold, unyielding fury which seemed to transcend injury and death even more than the fame of the Legiones Astartes proclaimed. Dark-armoured bodies shorn of limbs or severed in half by mauler cannon still dragged themselves onward to the attack, while tanks which should have been rendered inoperable thrice over by damage hauled themselves on as burning wrecks, their weapons still firing even as their own munition stores began to cook and detonate. The Xanite battle-automata were set upon by crawling phosphex and enervated by rad missiles, weakened prey before the marauding talons of Dreadnoughts which tore them limb from limb or pounded them into ruin. The vengeful fallen pressed on, there was no attempt made to secure the port facilities or to consolidate a line of battle, the army's imperative was simply to destroy, to kill and keep on killing, until they themselves were slain. By the time the Vodian Consistory, reeling from this fresh assault, realised the true danger of what was happening, it was too late. The breakout was underway and the invaders could not be contained.
Slowly but inexorably, the invading Legiones Astartes spread through the upper reaches of the forge-fanes, massacre and mayhem their only strategic goal. Savants and soldiers, servo-thrall and battle-automata, Tech-Priest and slave; all were left slaughtered. In their wake fires burned beyond control, crawling phosphex seeped through ventilation shafts and ate hungrily at anything it touched, power transition systems were blasted and sabotaged, fuel lines set to blaze and vox towers toppled. The surface levels of the great forge-fanes of Xana began to burn.
By the fifteenth hour after open hostilities had begun, the Xana System was awash in flame and spiralling wreckage. The remaining Xanite war fleet, which had engaged the Amphion's battlegroup, was now hurtling back to Xana II. The Mechanicum fleet was now about a third only of its early strength, having sustained further heavy losses in disengaging from the Loyalist capital ships, which had used their remaining fire ships against them as they tried to withdraw. The surviving Loyalist battlegroup, including the battered but unconquered Amphion, did not pursue, instead taking the opportunity to disengage themselves, their own arsenals having been all but exhausted by the protracted void battle and each one having sustained great damage from the fight. In the debris belt of Xana I, now aglow with burning hulks and torn by storms of exploding munitions, the outcome for the vast arms fleet had been even more disastrous as more than two thirds of the macro-transports had been either destroyed outright or sent burning to plunge into the gravity well of the gas giant or to tumble helplessly into the void. The architects of this disaster, the Dark Sovereign and the Legiones Astartes of the Ist Legion, were also departing for the system's edge, one of the great barques and the dromond Mu-571, now the Dark Angels' prizes, struggling to keep up with the warship's escape velocity. The fires raged also on the surface of Xana II, though now the whole Forge World had risen up against the invaders they had allowed into their midst.
Of the three great forge-fanes, only Setna had come through its attack all but intact; the invaders having penetrated as far as the vast, sub-surface galleries before being met by Setna's most bellicose guardians, a contingent of Knights of House Malinax, long veterans of war far from Xana's soil. Here the grim Legiones Astartes had been met by a score of Mechanicum-patterned Knights, and though nearly half of the Knights present had perished in countering the onslaught, the invaders had been burned and crushed in their hundreds, the fighting halting only when the last of the Space Marines had been bodily broken beyond whatever bitter thread of life propelled it. The other two great forge-fanes of Xana had not fared so well and of the two, famed Tephra had suffered greatly, with one of its mighty reactors breached and detonated, rending several square kilometres of its heart into radioactive slag at the cost of tens of thousands of lives lost and vast resources of machinery destroyed before the invaders were finally overwhelmed through sheer weight of numbers. The damage to its sister forge-fane of Escorial was not as great, but widely diffuse, the enemy having spread to its tangled arteries of tunnel-way and gantry, and the last remnants of the invaders, though reduced to a mere handful of ruined bodies, were still causing havoc in the depths.
Matters on Xana-Tisiphone had ended in an even bloodier state, the prison-forge itself having fallen under the assault of the Loyalist Legiones Astartes under Endryd Haar's command and the firepower of the captured Ordinatus, the population descending to violent anarchy and revolt which further allowed Haar's forces to ransack the weapons testing facility there before being suddenly and savagely beaten back by a counter-attack from below. The forces which assaulted them, brazen-armoured Legio Cybernetica cohorts, had slumbered deep beneath the Sheaol penitentiary and were strange, hitherto unknown patterns whose almost diabolic appearance was at odds with any recorded Mechanicum pattern. Moving with unheard-of speed and predatory instinct, these battle-automata drove back the Loyalist Legiones Astartes, killing many and forcing a retreat when all that the Loyalists had gained was soon endangered, the counterattack culminating when one of the prized Ordinatus, the Nepothax, was assaulted and destroyed in an attempt to recapture it. Reluctantly Haar's forces withdrew, taking their surviving prizes with them and departing the planet, their ship, the Tyrannis, herself sustaining heavy damage in her escape, barely outrunning the returning Xanite fleet.
The Xana Incursion was over.
The operation known as the Xana Incursion remained a secret of the Age of Darkness, one more battle fought unremembered and largely unknown, although a battle stranger than most, and ever afterward it has been an engagement shrouded in sinister mystery and rumour. The great provender of Xana, a bounty that may perhaps have tipped the war for either side, had been delivered into the hands only of death, save for a select portion which it is believed the Loyalists would use to their own ends during the Titandeath and the Siege of Terra itself, although the true gains of this victory or whether they were worth the great cost it took to achieve them is a judgement none can now make. Of equal enigma was the means by which the victory was gained, and in particular the true nature of the "army of the fallen," which was used to such lethal effect in the seemingly suicidal attack on the Forge World itself.
Ultimately, the alliance of Xana with the Traitors' cause had not been thwarted, only delayed by years, and perhaps that was enough. The Xana which was rapidly rebuilt and re-fortified and finally began to supply the Traitors with a great perfusion of ever stranger and more savage war machines in the Horus Heresy's final years -- a true example of what became known as the Dark Mechanicum -- was hardly recognisable from what had gone before and charged a heavy price for its support. There are some who have gone so far as to opine that in toppling Xana's existing ruling synod, the Vodian Consistory being murderously deposed from within the Forge World's own ranks soon after the incursion, a far darker and more dangerous order of masters was caused to come forth. And that they took what was left on the battlefield and used it for their own infernal ends, meant it was the Imperium's own deceit and savage weapons that gave rise to the nightmare that was to come.
- The Horus Heresy - Book Six: Retribution by Alan Bligh, pp. 55-81