Treachery at Port Maw



The Treachery at Port Maw was a notable event and military defeat for the Imperium of Mankind that was situated during the earliest years of the Horus Heresy and what was later on designed as the Manachean War. It was by the twin-assault of the Traitors on Hive Illum and the Armada Imperialis Port Majoris of Port Maw that the Manachean War was concluded, marking the end of the powerful system that had been the Manachean Commonwealth and the establishment of the first Traitor-held domain. As far as the dire events of Istvaan III and Istvaan V revealed Horus influence within the Legions of the Legiones Astartes, the Treachery at Port Maw is a testimony to how far Horus' treason ran within every other organisation -- military and other -- of the Imperium. To Imperial historians, the Treachery at Port Maw-incident marcs the beginning of a shadow-war that has run its course for the last ten millennia, a fifth-columnist's and traitor's war that has since then become the hallmark of an other Legion of Traitors: the Alpha Legion.

A Muster for War
The Manachean Commonwealth was an independent dominion forming its own self-governing sub-sector within the Imperium to the galactic east of the Cyclops Cluster. Considered the lynchpin of the Coronid Deeps, it was also the principal axis of Imperial power holding the northern border of the Imperium together thanks to the dual influence of two systems: Manachea itself - principally the Hive World of Manachea Vysidae, which was in terms of population and industry the equal of any of the great Hive Worlds of the Segmentum Solar, and Port Maw which, while still under construction and expansion, was one of the most powerful Imperialis Armada bases in the northern Imperium. This border sub-sector, geared as it is for war, presented a formidable obstacle to any attack contemplated against it, and few regions outside the heartlands of the Segmentum Solar could claim to be so well protected.

Port Maw itself was home to a very sizable fleet, numbering some hundred and seventy capital and line vessels of the first rank, and nearly a thousand other warships of lesser degree, whose principal purposes were to patrol the nearby Segmenta within the borders the Great Crusade had established., defend its worlds from attack, maintain order and enforce the writ of Imperial law. As part of this peacekeeping force, stationned there at secondary bastions in the Manachea and Numinal systems, were a combined army of one hundred and ninety-three Solar Auxilia Cohorts of the Imperial Army, forming an independant strategic command of the Excertus Imperialis under Grand Admiral Ospheus LaBray.In practical terms, this comprised notionally some 3'860'000 fully armed, equipped and disciplined fighters outfitted to the highest standards of the Imperium's human soldiery. As Solar Auxilia, they were trained and experienced both in void combat and planetary defence operations and represented a significant military force, even when set against the threat of a Legiones Astartes attack. Besides this elite army, the Commonwealth's own emergency defense planning was predicated upon the ability to quickly raise, arm and supply tens of millions of planetary militia in extremis, and this act itself did not seriously impact upon the massive economic output of the sector - such were the immense labour reserve of Manachea Vysidae and the war materiél its wealth had allowed it to stockpile. Nor was the Commonwealth entirely without the assistance of the Legiones Astartes, albeit in very small numbers. The limited garrison of Imperial Fists stationned in their bastion on Manachea Lux had quickly subdivided itself and sent its Legionaries to act as advisors throughout the Commonwealth, lending their expertise in counter-siege warfare to improve defensive structure and emergency action plans. However those of the Astartes that had managed to escape the deadly trap set for them on Istvaan V refused to submit themselves to"merely" human commanders and had pursued their voyage, grateful for the opportunity to regroup and reequip before moving on.

The question then immediately becomes why did this vast and mobile force not come to the aid of the Cyclops Cluster when it was attacked? The answer is a simple one; it was not allowed to. The Warmaster had not allowed it.

Long before the first shot was fired on Istvaan V, or even Istvaan III, the Warmaster had ensured that every centre of military of the Imperium he could not control or vanquish immediately would be temporarily neutralised as not to impede his firsts moves in the civil war. So it was that at the time of the Istvaan III Atrocity, numerous elements of the Port Maw Excertus had been deployed to the very edges of their usual far-flung operational range; tied down in chasing half unsubstantiated reports of privateers or xenos marauders, occupied on deep patrols or even temporarily reassigned to other campaigns or fleets in distant border regions of the Imperium -whether such reinforcement were truly warranted or not. With the authority of the Warmaster still absolute and uncontested, such actions didn't raise any suspicion or comment. When the rebellion became apparent orders were modified and warship squadrons and Cohorts of Solar Auxilia recalled at once for a grand muster at Port Maw, but this was a task neither swift nor easy. Marshalling troops also became increasingly more difficult as a great uprising in Warp storms and warp turbulences was noted which would only gain in intensity as the Horus Heresy unfolded. By 006.M31 matters became ever more dire for the isolated Port Maw Excertus as its fleet elements had spend much of the previous years all chasing shadows and were now confronted with a very real and terrible enemy. All across the Coronid Deeps reports of isolated and unknown warships, civil unrest, outlaw activities, unexplained calamities and xenos raids became ever more frequent - then came the messengers of the Warmaster, demanding the Dark Compliance of the Cyclops Cluster, the Grail Abyss and even Lethe within the borders of the Manachean Commonwealth. It was only a question of time until such an emissary would be send to Manachea as well...

Yet no emissary came, but that only seemed a small relief compared to the dire news that continued to reach Manachea. Many deep range patrols sent beyond the Segmentum border simply did not return, while raiders chaotically attacked Imperial outposts perilously close to the borders of the Coronid Prohibition Zone, an area of space where the authorities of Port Maw were forbidden to enter by ancient decree. These raids were tentatively attributed to the Rogue Trader Militant Rom Jhutlannder whose ships had served in the past as outriders and pathfinders for the Warmaster's own 63rd Expeditionary Fleet. However, when the anemy finally manifested itself, it would not be from the quarter expected, but from the western approach of the Commonwealth: a xenos-infested conglomerate of ancient ship-wrecks and trapped asteroids, a Space Hulk the which the Manachean Commonwealth had not seen in many decades -- the Orks had invaded the Vlorath Srader System.

The Enemy Unlooked For
In accordance with the Coda Navis the invading Space Hulk was designated Red Polyphemus and its unexpected appearance sent the Commonwealth’s military scrambling to respond. Space hulks are immense conglomerations of shattered planetary rock and ancient derelict ships whose navigation is notoriously unpredictable. It was thought at the time that the hulk had been drawn perhaps to the system’s potent Astrophatic relay orbiting the system's seventh planet. However, its appearance after a brief but violent storm in the Warp seems too doubtful in hindsight to be considered as mere ill-fortune.

While the Orks as a galactic-scale threat within the expansive celestial territory of the Imperium had been subdued by the Great Crusade, on the outer frontier of the Emperor’s domains, they still remained a potent if infrequent menace, and the degenerate, half-devolved breed that infested the Red Polyphemus represented the largest concentration of the brutal xenos encountered in the region for nearly thirty years. Such a dire menace required the immediate mustering and dispatch of an entire battle group from Port Maw to combat, diverting a muster of warships and cohorts intended to deal with the worsening situation in the Cyclops Cluster. By the time the Imperial fleet answered the attack, the Vlorlath Srader Relay was already overrun, and its tens of thousands mutated Orks and gyre-worms had made planetfall on Vlorlath Srader while the space hulk itself ploughed madly onwards, forcing the fleet into a dogged and bloody pursuit. In normal circumstances, the aid of a sizable Legiones Astartes force would have been ideally called upon to strike a death blow to the hulk, but in this darkening times, no such help was available. This left the Port Maw battlegroup the thankless and dangerous task of attempting to slowly pulverise the gargantuan Red Polyphemus with prolonged, close range bombardment, rather than board it and destroy it from within - all the time under attack by the barbaric xenos which infested it like vermin. Without the elite Solar Auxilia Cohorts of the Port Maw Excertus Command, dealing with this catastrophe would simply not have been possible, both in terms of the counter-invasion of the Vlorlath Srader system's colony worlds, and the defence of the taskforce attacking the Ork hulk, which faced continual suicide attacks and boarding assaults by the savage xenos and their crude but murderous void engines.

As the campaign against the xenos dragged on into the closing days of 007.M31, the hulk finally began to fragment under the bombardment, but the victory's cost had entailed a butcher's bill in lives and ships lost increasing with every report, while word reached Port Maw and Manachea of the fate that had befallen Lascal - the destruction of an entire battlegroup of the Port Maw Armada - and then Dominica Minor, offering a terrible blow to the Commonwealth's morale. The fears of the Commonwealth's defenders now had a name and a shape at last. Calls for military aid were passed on to still loyal territories to the galactic east in the Coronid Reach - the only part of the Imperium with which contact could be readily made now that the Astrophatic relay of Vlorlath Srader was lost to them. Grudgingly such worlds like Numinal and Agathon gave their accord, well aware that should Port Maw fall they themselves would have little chance to prevail on their own against this enemy. Orders for general mobilisation were issued, the final stages of emergency plans enacted, defences on the Commonwealth's eastern borders were heavily reinforced and known stable warp termini to and from the Cyclops Cluster were aggressively laid with void mines. Given the ongoing battle within the Vlorlath system occupying a major part of the fleet's strength, the order was given that task forces and patrols were to be recalled where possible from all other posts and rendezvous at Port Maw with the expectation of having to meet head-on what would once have been an unthinkable threat; the direct and massed attack of the Death Guard Legion from the silence of the Cyclops Cluster.

It was, unfortunately, all just as the Warmaster had planned.

Treachery
The situation in the Port Maw system was one of extreme and ruthless order holding back a tide of chaos. The shell of the great artificial planetoid on which the vast naval base and void-forges had been built was choked by a swarm of vessels, both mighty and small, from a score of battleships girding themselves for war, to dozens of cruiser squadrons, countless hundreds of escorts and thousands of servitor-drone tenders, victuallers and supply ships, troop transports and orbital lighters - all about their own business as the entire system stood on a state of high alert. In grim alliance, reinforcing fleets had come from the east, dark bronze warships bearing the fiery lantern-sigil of the Agathean Domain, one of the most isolated of all of the Imperium's clusters of civilization, lean pirate-killers from the Cerada Nebula and a trinity of huge storm-grey war-arks from the Mechanicum Forge World of Cyclothrathe, void-automata scuttling across their hulls like macabre insects.

Into this morass of vessels, before the border fell silent, had also come the refugees from the storm. Some had been mercantile vessels, other great livestock conveyors or ore transports, fleeing from a dozen different systems under threat or under attack, and other were warships, the ragged survivors of the battles in the Cyclops Cluster and a handful had fled from as far afield as the murderous void battles at Istvaan, but of these no Space Marine vessels remained long at anchor. Of this floathsam of war, most had been mauled by the enemy or driven past any safe operational ability in the desperate flight to reach safety, and all required aid and assistance of some kind. Some even had arrived in such a parlous state that they had to be scuttled or set to drift at the system's edge so they posed no danger to the vortex of ships that swirled around the port station.

This hurricane of vessels, with its complexity and ever-shifting maze of hazards, was far too great a burden than any merely human mind could bear, and control of the vast armada was chanelled through Port Maw's Mechanicum Astra Contol Panopticon. This powerful broadast tower, ten kilometres high, jutted spike-like from Port Maw’s southern pole. From here fleet orders and beacon signals were relayed, navigational co-ordinates checked and rectified, and centrally controlled cogitator-maintained data directly fed into the helms of the ships under Port Maw's watch, so as to swiftly reorganise their patterns and avoid collision. This system could, of course, be swiftly overridden by the ships themselves, but still represented a terrible vulnerability and so the Panopticon's control frequencies had been proofed against treachery by a complete replacement of cyphers and encryption-djinn following the reveal, first of the Warmaster's treachery, and then changed again with panicked haste after the double blow of yet more betrayal at Istvaan V. This had been of even greater concern as a significant portion of both the Raven Guard and the Iron Warriors fleets had made layover for resupply at Port Maw on their way to what would become the Dropsite Massacre, and both had been fully updated on the Port's codes and deployment schedules. All of this was deemed compromised and once again swiftly replaced wholesale and, due to this, the Port Maw void augury and geas-override systems were believed by the Armada Command to still be impregnable against outside influence. Indeed, perhaps they would have proved so, except that the spider at the heart of this vast web, the Archmagos Leit Mercuric, cyber-ordinator of Port Maw, was already secretly sworn to Horus.

The Web of Deceit
Under the hand of the treacherous Archmagos of Port Maw, a fiendish web of conspiracy and malevolence had been forming and its strands stretched far and wide across the Manachean Commonwealth and its worlds, and out to dominions of Agathon and the dual suns of Cerada at the furthest extreme of the Coronid Reach. Now its hour was at hand.

This conspiracy had many layers, and many agencies were bound up within it, from the Traitor Archmagos-Astral Mercuric and her acolytes, to several officer cadres of the Imperialis Armada who had been corrupted by strange rites and secret societies brought into their midst while serving alongside the Sons of Horus and the Word Bearers Legions, to turncoats bribed through the more traditional means of festering dissent, greed, fear and hungry ambition, and purposefully planted spies and saboteurs hiding behind identities of murdered men and women.Their numbers, particularly in relation to the billions of men and women under arms in the Manachean Commonwealth, were in comparison very few, but they were well placed, and within such a tainted network, it had been all to easy to ensure that forces and agents loyal to the Warmaster were where they would do the most harm when the time came.

Like a fruit, wholesome to the appearance but canker-ridden from within, the Manachean Commonwealth's vaunted defences were already undermined, and its fate was to serve as an object lesson not in outright destruction -- as that at the worlds of the Cyclops Cluster had been - but in the surety of a blade in the back.

The Song of Chaos
At Port Maw, in the flickering actinic light and glimmering brass of the Mechanicum Control Panopticon, a countdown set in motion long before wound down finally to zero. The Mechanicum data-djinn web blazed with a power unheard of, and all over the system vox-circuits burned out, auguries were suddenly shrouded in static and auspex scanners shut themselves down as if to avoid the flash-flare of a nova. The vast swirling fleet that surrounded the Port station was in a moment all but blinded, and in that same moment, the navigational net entrusted to sift safe order from chaos began to lie. Ships collided without warning, showering wreckage in the paths of others, drives flared suddenly to full power, hurling the crews of the runaway vessels to bloody pulp, pulverised by the unexpected and unguarded against accelerations, and flag bridges were swamped with hostile scrap-code.

On a hundred vessels, systems failed or misfired as the chaotic signal continued to pulse, and in the others whole decks depressurised or vented into the void, dragging their silently screaming inhabitants with them. The worse calamities the deadly electromagnetic song inflicted though befell upon only the lesser vessels; the merchantmen and the light escorts without the power to resist and to whom an end came swiftly. The greater warships were far too powerful and too resilient to suffer much other than debilitation and confusion from this data djinn-borne blade in the back, their own fearsome machine-anima immediately reacting against the attack, over-riding or burning out corrupted systems to regain full control. But as they recovered, many of these leviathans of war found themselves suddenly under fire from those they believed allies. For while many reeled, there had been warships prepared in secret for this assault and others against whom the attack had not been directed at all, and at whose helms Traitor hands had mastery. Already warships had begun to burn as former comrades opened fire at point blank range before they were aware of the of the danger - laid low by treacherous strikes intended to cripple rather than kill. Within tightly formed squadron formations, vox-broadcasts demanded surrender and some vessels, finding themselves surrounded by turncoats and all but powerless, could do nothing but comply, but elsewhere the initial attack had been anything but successful in subduing those ships that remained loyal, and aboard these, void shields swiftly ignited and alarm sirens sounded as battlestations was called with vengeful ire.

On the vast conglomerate station complex that was Port Maw itself, fighting had already broken out between Traitor and Loyalist, the station’s provost marshals having thwarted an attempted mutiny within their own ranks were now rallying armed resistance to lay siege to the Mechanicum Control Panopticon, which would answer neither vox-hail or override command, and was undoubted source of the malign broadcast drowning out all others. The frantic provost marshals, unable to make headway against the automated defences which ringed the Panopticon citadel, gave way to the elite white-armoured Veletaris sections of the 905th Lethe Cohort, the "Ash Scorpions" as they had come to be known. Veterans of a dozen of ferocious war zones, the discipline of battle had turned these feral-worlders into a lethally effective fighting force. Blasting through bulkheads with Melta bombs and tracked Rapier cannon, they worked their way corridor by corridor, cutting down any resistance they met with savage crossfires of Volkite rays, and forced a passage through the Maw’s labyrinth of tunnels towards the generatora which supplied the Panopticon with its power.

As they battled closer to the Mechanicum section, matters became yet more desperate as the station’s fabric itself seemed to turn against them and they were forced to bring up flamer units to scour the passageways of scuttling haemonculites and darting Servo-skulls, driven in frenzied attacks like maddened animals. Breaching their way at last into the great generator vault, they found a vast cathedral like space, dominated by five enormous, lightning-shrouded plasma coils, each as large as a battle Titan. Here stood the acolytes of the treacherous Archmagos-Astral Mercuric, hulking Tech-Priests as heavily armoured as Legiones Astartes Terminators in order to endure proximity to the radioactive infernos they tended, metre-wide steel spiders which leered with the rictus-dead grins of human skulls from the gantry-ways and webs of cabling that festooned the vault, and scores of blank-eyed servitors, their flesh scorched cinder-black. Beyond all these, guarding the central control pulpit, was a maniple of iron-grey Castellax Battle-automata, their Bolt Cannon levelled and cycling; a deadly barrier beyond which nothing could pass.

Battle was joined. The fate of Port Maw hung in the balance, bravely the "Ash Scorpions" advanced into heavy fire, rushing from cover to cover as fast as they could as they tried to find a way through the tangle of consoles and companionways to the heart of the generatora. Soon the cavernous vault was filled with a hurricane of shrieking energy blasts and roaring bolt shells. Machinery exploded, companionways buckled, acrid smoke filled the air. Men and automata were cut down alike, steel claws found flesh and bit deep, flamers gouted their hot breath, grenades clattered and thundered, shredding bodies and sundering metal. Amid the storm, the wall of Castellax stood unbreached, their armour scorched and smoking as blasts and shell washed over them like hail across stone until a trio of tracked Rapier batteries emerged from the smoke, the shearing beams of their laser destroyers converging on the lead Castellax and sending it to burning oblivion. Sensing that their moment had come, the Veletaris storm sections broke from cover, screaming the ancient blood-cries of their Feral World, and charged the breach in the lethal barricade of Battle-automata. Dozens died before they reached it, torn to pieces by the fury of the Mauler Bolt Cannon of the surviving Castellax, while other were pulverised by the heavy blows of their servo-claws, but like a pack of raptors they swarmed the armoured behemots, volkites spitting hellish rays at point blank range into joints and tears in the Battle-automatas' armour. Another of the Castellax fell, thrashing in blind rage as its legs were cut from beneath it, and the Veletaris surged through, crashing into the Tech-Priests with a strength born of desperation and sacrifice that could not be allowed to be in vain.

Only a single Veletarii Prime, whose name has gone unrecorded, managed to force his way through the tumult and slaughter to the dais of the control pulpit, his void armour blood-splattered and aflame. With no time for thought or plan of action, he plunged his power sabre directly into the heart of the machine, even as vast steel claws were fastening themselves around his pressure helm. The pulpit dais exploded in a blazing white fireball, murderous arcs of lightning shot from the great plasma reactor cores, ravaging the vault as their emergency protocols engaged, and the mis-directed power was vented into the capacitors which lined the wall, burning men and machines caught between them into clouds of cinders.

The interference signal blanketting Port Maw first faltered, and then failed.

Triumph and Betrayal
In the void-space around Port Maw, sudden deafening silence cut trough the incessant pulse across the vox and signal network of the Loyalist ships, and in its wake matters immediately became less chaotic and more murderous. as battle line were swiftly drawn between friend and enemy, hails sent and answered, ultimatums and demands for surrender issued and spurned, and command asserted in the face of the crisis.

Aboard the titanic Triumph of Reason, the Port Maw Armada flagship -- a huge fleet control vessel re-forged from the twin hulls of two Legatus-class macro-battleships crippled in the earliest years of the Great Crusade -- the attempted assassination of Grand Admiral Ospheus LaBray had been thwarted, and an attempted mutiny eradicated with bloody certainty. LaBray was now once more in command of the immense warship and with the malign signal countered, the auguries and strategium-luminators systems of the Triumph -- designed to order and direct an entire Segentum fleet-of-war if needed -- reasserted tactical control over all Loyalist vessels that would answer its call. LaBray’s first order was to the Dictatus-class ram-battleship Kurga, which hung in orbit near the Port Maw station, having just similarly suppressed a mutiny of its own. Awakening to war, it powered towards the now silent Mechanicum Panopticon tower, the six kilometres long armatures of the ram-battleship’s triple servo-claws extended. The Kurga smashed into the tower, the thirty metre long teeth-spikes of its claws piercing its armour and sinking slowly through its guttering power fields, and were joined moments later by scores of rocket-fired melta-barbed harpoons which speared into the brazen faces of the tower. Its victim secured, the Kurga’s drive burned white hot. The ten kilometre tall tower shivered and cracked, resisting defiantly against the unimaginable forces tearing at it, but soon shuddered and gave way as it, but the Kurga’s oversized engines burned like hellfire. The tower broke, a myriad of secondary explosions rippling along its length as it crumbled like rotten wood and was dragged free into the void. The malign signal would not sound again.

At the centre of the maelstrom of ships, Loyalist and Traitor vessels began to break apart, guns firing in fitful bursts, uncertain of friend and enemy. On the outer edges of the vast slow vortex of ships, tens of thousands of kilometres from Port Maw itself, the outrider of the great armada were only just recovering. These vessels had not been part of the core fleet at the Maw, and comprised dozen of reinforcement squadrons sent to the muster from other systems, along with numerous refugee craft and mass conveyors, around which were small provender and repair vessels that flitted like tiny sea creatures swarming around ocean leviathans. Here, removed from the heart of the treacherous attack, the carnage had been less extreme and the mutinies fewer, but still anathema signal from Port Maw had blinded and deafened them for a time, and now most were bewildered and uncertain of just what the catastrophe unfolding before them meant, uncertain of who was firing on who, or why.

At the outermost edge of the maelstrom of ships, and all but unnoticed in the confusion, one of the great war-arks of Cyclothrathe, which had so far taken neither side in the anarchy, now triggered its manouevre jets and came about. The colossal barrel-shaped vessel slowly turned and pointed its prow towards the opposite edge of the spiral arm of outer ships to the still unengaged warships of the cruiser squadron sent from distant Agathon to answer Port Maw’s call. Not one of these vessels bore a Traitor inside and to them the battle yet had no seeming cause and no clear side to choose. The Cyclothrathine war-ark, designated Arithmetic of Violence, silently broke apart, its ten kilometreslong hull plates separating like the petals of a colossal flower in the storm. Revealed within in place of internal decks were row upon serried row of inert void torpedoes, which, as if lit by a single torch, ignited their plasma drives with a golden blaze of fire. They burned across the void to the Agatheans, smaller ships caught in their path obliterated instantly, and struck home like the obliterating fist of a god. The sudden searing flash of a score of mighty warships dying at once in fire was so bright that in that instant it burned visible to the naked eye even to the dark edges of the system's Ort-cloud. And there in answer, a gigantic black warship came to life.

The Ravens
At the same hour that the first footfalls of the Titans were sounding at Hive Illum on Manachea, at Port Maw open void battle had now erupted between those ships that had turned fully traitor and those who had remained loyal, while all across the artificial planetoid station below them, civil war was being waged with bloody conviction. The Traitor’s plan had proved only partly effective in conquering the Loyalist fleet from within or forcing its surrender, and now the maligtn influence radiating from the Mechanicum Panopticon had been ended, the Loyalists were rapidly gaining strength.

After the bloody and chaotic skirmish, those warships that remained mobile had broken away and parted in two battle lines, forming thousand kilometre-long crescent formations mirroring each other in ortbit round the Maw each now staying their range and keeping the bulk of the artificial planetoid between them and the enemy as they manouevred to form up. Around them hundreds of wrecks and stricken ships cascaded, reeling with damage or drifting paralysed as bloody struggles raged on within them for control. Neither force had such overwhelming superiority yet that a direct attack on the other would guarantee victory without severe losses, but both knew that to attempt to flee - to turn away from the enemy and run - would be to secede the entire strategically vital star system and all it contained to the enemy. The fate of Port Maw and its vast armada hovered on a knife edge.

As the two battle lines fell into a deadlock, from the darkness of the outer system came a new and unexpected threat. The dark fleet answered no hails, broadcast no identification cyphers, but came hurtling on at near relativistic speeds like a dagger hurled at the heart of Port Maw. In the strategium of the gargantuan Loyalist flagship, the Triumph of Reason, Grand Admiral LaBray awaited impatiently as his sensorium officers strained their auspexes to get a firm report on the incoming fleet. Some form of masking technology was being employed that scattered and defused the scanning beams, making a definite fix on the vessels impossible to attain. LaBray likely knew, as many of his rank did, of the rumours of such arcane devices being employed by the secretive Raven Guard Legion - a Legion which remained loyal, but was reported destroyed at Istvaan V. Could this be a Raven Guard splinter fleet, the survivors of that cataclismic battle? If so why did they not answer, why did they not identify themselves? These questions could not be readily answered. But however effectively their true nature was shrouded from LaBray’s auspexes, while operating at such intense acceleration, their engines burning bright with plasma thrust, they could not hide their number; there were twenty vessels by their drive flares, at least half of which were capital class by his savants’ estimations, meaning LaBray’s own fleet outnumbered the interlopers by a margin of four for one. It was a force which alone he could overwhelm, but if it joined with the mass of the enemy now matching him in orbit on the other side of Port Maw, would likely tip the balance in the Traitor's favour. Without hesitation LaBray gave the order, and the vast crescent of his armada turned and began to arc toward the stranger-fleet on an intercept vector, their own engines burning bright.

The distance closed, thousands of kilometres flashing by in mere seconds, and behind the Loyalists the Traitor fleet followed suit, but it would be LaBray’s ships that would meet the newcomers first, that was now inevitable. The minutes ticked by until it was reported that the incoming ships were now close enough to be within visual range of the flagship’s occularis, and LaBray immediately ordered the image up before him. It was only then that he realised the depth of his mistake. The vanguard of the incoming ships were indeed Legiones Astartes Battle Barges of the Raven Guard, or at least had been; two modified Dagon-class Grand Cruisers bearing the sable heraldry of Corax’s Legion now torn and burned in the fires of battle, but what came after them was not of the Raven Guard. The monster rose up behind the battle barges, making them seem as mere frigates in comparison to its nightmare magnitude. It was a ship no Imperial captain could ever have failed to recognise at first glance, it was a war machine few vessels could ever hope to match, but what its presence portended was darker still. It was the Vengeful Spirit; it was the flagship of Horus.

Conquest
The warships of the Sons of Horus cut into the Loyalist battle line at its apex, smashing into it head on, the turncoat warships of the Raven Guard being sacrificed to soak up the fury of the Loyalist guns as they closed. The Traitor spearhead of warships cut into the Loyalist fleet like a lance, piercing it bodily- splitting the Loyalists’ defensive formation in two like an axe cleaving meat.

At the apex of the spearhead, the Vengeful Spirit came on through the blast waves of flames and debris ahead of it like a beast of ancient myth made real, its armoured prow smashing aside Loyalist cruisers like toys, its many-decked broadside batteries smashing shields and cracking open hulls with contemptuous ease as it passed. Along its darkly amoured flanks, strange symbols writ as if by a colossal hand seemed to flicker and fade, as if pulsing to some terrible heartbeat and the void around it appeared to twist and recoil. The juggernaut-ship plunged on through the Loyalist vessels, dealing death as it went, unstoppable. The gargantuan Battle Barge of Horus had one goal, one true target; the Triumph of Reason protected at the heart of the Loyalist armada, and the focus of its command and control.

Its quarry in sight, the Vengeful Spirit made as if to ram the vast double-hulled Triumph of Reason, bat as it closed - the guns of both hunter and prey balzing savagely - the Vengeful Spirit's engines flared and it spun suddenly on its axis - a manouevre which at that velocity should have been fatal for any ship of its size - the manic and unexpected turn smashing to dust two hapless escorts that found themselves in its path, while a bastion frigate that caught the full blast of the Vengeful Spirit’s engines as it swung was flung burning into the void. The space between the two gargantuan warships seemed to distort and shudder as the ship of the Warmaster violently arrested its progress so that it now flew above and alongside the Triumph - matching her course and velocity. In response to the seemly impossible manoeuvre and the threat now looming vulture-like over the Thriumph, the lumbering giant below her tried to throw herself aside to evade what was to happen next or at least try to bring her own broadside to bear, but she was too slow and it was too late.

Vortex missiles, rare and deadly weapons of the Dark Age of Technology, spat from the Vengeful Spirit’s broadside launch tubes and ecploded in ghostly spheres of silent nothingness that tore away the Triumph of Reason’s void shields like paper and cracked open the decametres-thick hull plating beneath them like splintering ice.

Notable Vessels

 * Triumph of Reason (Unique Battleship, Unknown Class) - The Triumph of Reason was a vessel with a long and twisted history. Built from the wrecked hulls of two prior Legatus-class battleships that had been mauled early on during the Great Crusade, the Triumph of Reason was easily the biggest ship in the entire Segmentum Obscurus Armada. Rebuilt after an unique pattern, the Triumph of Reason was designed from the start to become the flag-ship of the entire Segmentum Armada and much weight and space was given over to communication and auspex devices. Stationed at Port Maw for the greater part of its career, placed under the command of Grand Admiral Ospeus LaBray for much of its early years, the Triumph of Reason was equipped with countless cryo-chambers to harbour Ogryn Charonites, the only troop at the admiral's disposal that would prove superior to traitorous Legiones Astartes in case of boarding actions. The Triumph of Reason would participate in the early hours of the Horus Heresy at the notable Treachery at Port Maw where it would assume control and command of the entire Port Maw Armada and its allies once the destruction of the Mechanicum Panopticon at the heart of the treachery had been confirmed. It would be from the bridge of the Triumph that Grand Admiral LaBray would coordinate the battle against the Sons of Horus fleet, even engaging the lauded Vengeful Spirit of Warmaster Horus himself. Outmanoeuvred by the Vengeful Spirit, the Thriumph of Reason came under attack by Sons of Horus boarding parties and even the Archtraitor Horus Lupercal himself after the first assault wave had been nearly thrown back by the hundreds of Charonites held in the Triumph's borrows. Seized from within and with LaBray being killed in his failed attempt to escape ship, the Triumph of Reason would remain at Port Maw for the following  years of civil war, its communication hub needed to replace the destroyed Panopticon. The once proud Imperial vessel became a glorified if macabre throne room for Horus' chosen regent, a Sons of Horus line captain by the name of Taloc Thorne, which renamed the battleship "The Lash" and took the title of Tyrant of Port Maw.
 * Vengeful Spirit (Gloriana-class Battleship - The Vengeful Spirit was a towering Gloriana-class Battleship modified to confirm to the Scylla-pattern and that served faithfully as the Luna Wolves' - and later the Sons of Horus' - flagship during the entire Great Crusade. As flagship of the XVIth Legion, the Vengeful Spirit was also the personal ship of Warmaster Horus Lupercal, harbouring his command centre and throne room, it's hull being adorned by the Warmaster's own emblem; the Eye of Horus. More powerfully armed than nearly any vessel in service of the Emperor, the Vengeful Spirit would become a dreaded sight during the dark years of the Horus Heresy, preying on Imperial systems on its powerful engines with made the colossal battleship a far quicker predator that most readily believed. By the time of the Manachean War, the Vengeful Spirit 's transition to a flying temple to the Dark Gods had already begun, its once proud hull defaced with ritual and esoteric symbols several hundreds of feet wide and in all likelihood painted with human blood. Present in the second part of events known as the Treachery at Port Maw-incident, the Vengeful Spirit would lead the Sons of Horus into the developing battle between Traitors and Loyalists of the Port Maw  Armada. Approaching covertly behind two captures Raven Guard Battle Barges, the Vengeful Spirit would almost immediately head for the Triumph of Reason, the loyalist flagship which it badly mauled before sending boarding parties to capture the pride of the Port Maw Armada. The Warmaster himself would be forced by necessity to join the boarding actions as his troops where being slowly overwhelmed by rampaging Ogryn Charonites Grand Admiral LaBray had released as last line of defense. Turning the course of battle by himself, Horus was however denied the satisfaction of slaying the Grand Admiral himself. The Vengeful Spirit would swiftly leave the Port Maw-system carrying the Warmaster all his way to the Battle of Terra and his final confrontation with the Emperor of Mankind. The Vengeful Spirit still roames the galaxy, having found refuge in the Eye of Terror with the Black Legion of Abaddon the Despoiler.
 * Arithmetic of Violence (Mechanicum War-ark, Unknown Class) - A gigantic vessel of nearly ten-kilometres length, the Arithmetic of Violence was only one of a trio of such vessels present at Port Maw during the events of the Treachery. Secretely in league with Horus for many years, the Cyclothratine Mechanicum had infiltrated the Port Maw muster under the guise of loyal servants of the Emperor. When the blanketing signal was released from the Mechanicum Panopticon Tower, the Arithmetic of Violence used thesurrounding pandemonium to manoeuvre itself into perfect launch position for its devastating complement of plasma-torpedoes. Blossoming like an unholy flower, the Arithmetic of Violence shed her long hull plates and revealed row upon row of void torpedoes that annihilated the allied fleets of Agathon, Numinal and the Cerada Trinity in a single devastating volley - for their crews and captains had not been corrupted or infiltrated and remained staunch loyalists to the Emperor. Yet the Arithmetic of Violence failed in its task as one lone survivor - the Telemachus - remained and would escape from the system to carry news of this betrayal to its home world.
 * Kurga (Dictatus-Class Battleship) - The Dictatus-class was an ancient class of ram-battleship that had slowly become obsolete as the Great Crusade wrought on. The Dictatus-class were almost primitively barbaric in their design as their main role was to ram enemy ships and shred their hulls like an ancient seaborn predator with their enormous jaws - a tactic that seems more suitable for the dreaded Orks than the Emperor's soldiery. Mounted on a set of hydraulic platforms these triple gigantic servo-claws - each one of them nearly six kilometres in length -- compromised a row of nearly thirty metres long teeth-spikes, while its "mouth" supported scores of rocket-powered melta-barbed harpoons not unlike the more massive Ursus Claw that were the pride of the World Eaters flagship, the Conqueror. The Kurga was present at the Treachery of Port Maw from which it remained one of the few Imperial ships that succeeded in making good its escape despite having to crush a mutiny on its board. It remains famous to this day for having shred and ripped off the Mechanicum Panopticon tower which traitor elements had used to sabotage the Armada's communication netwok and targeting arrays. The Kurga would go on to fight with distinction in the years after the Treachery, its powerful drives and unorthodox tactics proving a valuable asset in the dark years to come.
 * Telemachus (Unknown Class, Cruiser) - The Telemachus and her sister-ships -all veterans of the former 60th Expeditionary Fleet - answered Grand Admiral Ospeus LaBray's call after the costly destruction of the Space Hulk known as the Red Polyphemus. Battlefleet Agathon send an entire squadron of cruisers to the gathering armada at Port Maw. The Telemachus ' captain was none other than Jocasta MaSade, grandaughter of the famed Ireton MaSade, former Imperial Commander of the Agathean Domain and future hero of the Imperium. The Telemachus was the sole survivor of the eight Agathean cruisers send to the great Armada Imperialis muster at Port Maw, its sister-ships all falling prey to the treacherous attack of the Arithmetic of Violence during the infamous Treachery at Port Maw-incident. This single act of violence would trigger a gruesome war of vengeance between the forces of the Agathean Domain and those of Forge World Cyclotrathe. Despite her wounds, the tenacious Jocasta MaSade refused to leave her bridge, ushering her crew to fight on. It was only once the Telemachus had escaped the trap set for her that Jocasta MaSade let herself be examinated. Alas by then the damage had been done and the valiant captain died from blood-loss. The arduous journey back home would however set events in motion that determined the Agathean Domain's participation in the Horus Heresy.