Port Maw - Treachery: For all intent and purpose, the Aestellica System had become a fortress, a citadel of Imperial might that would hold out against the Traitor -- or so the Port Maw authorities at least thought; for they had failed to anticipate that even the mightiest fortress can fall from the inside. Unbeknown to Grand Admiral Ospeus LaBray, the Imperial muster at Port Maw had been infiltrated by agents of the Warmaster.In a conspiracy of unforeseen magnitude whose many layers and ramifications had stayed hidden, a shadow network had established itself, worming its way into nearly every sensible position.Even the grand admiral's own flagship, the imposing Triumph of Reason, harboured countless Traitors as did many other vessels that had heeded the admiral's call to arms. Chief amongst these Traitors was the Archmagos-astral Leit Mercuric, Cyber-ordinator of Port Maw's Panopticon.The Mechanicum Astra Panopticon tower was a ten-kilometre-high transmission and broadcast tower, whose powerful antenna pierced the sky at the southern pole of the planetoid.The Panopticon regulated in-system traffic so as to ensure that no collisions impeded the daily work of the countless vessels, transports, supply ships and tenders that Port Maw needed to function.It also doubled as a central communication hub for the Port Maw Armada, relaying fleet orders and checking navigational coordinates.There a secret countdown was set in motion, designed to coincide with the arrival of the Sons of Horus' vessels in the neighboring Manachea System. As the countdown irremediably reached zero, the hand of the Warmaster was revealed.No warships of his Legion or the feared Death Guard presented themselves at the outskirts of the system, only those forces of the Mechanicum and the Armada Imperialis secretly sworn to Horus would deliver Port Maw into his waiting hands.Suddenly, malignant data-djinns filled the communication channels, burning out Vox-channels, shutting down auspex arrays and overcoming the Machine Spirits of lesser escorts and merchantmen vessels, altering their course to crash, sending Plasma Reactors into overdrive or triggering unforeseeable accelerations which turned the unprepared Human crews into a fleshy pulp.The larger warships of the Armada suffered little from this cyber-attack, but as a result of the mayhem the fleet was in a dire state of chaos, capital ships deprived of communication and escort craft scrambling for orientation.The cyber-attack was the signal Traitor agents and fifth-columnists had been waiting for to spring into action. All across the fleet mutinies and revolts erupted amongst the Port Maw facilities, the ships' crews and even the Triumph of Reason's and the Kurga's decks.Grand Admiral Ospeus LaBray's elite Veletarii Life Guard barely stopped an assassination attempt on the Armada's commanding officer, while on some ships purposefully spared by the data-djinns weapons opened fire on their "comrades," their Traitor captains seizing on the confusion wrought by the data-djinns to inflict maximum damage on Loyalist ships.Everywhere, battle between Traitors and Loyalists was joined. Port Maw's own peacekeeping force, the Armada provost marshals, reacted the quickest, both thwarting a mutiny within their own ranks and discovering the point of origin of this malignant cyber-attack: the Mechanicum Panopticon Tower.Quickly the provost marshals organised a proper siege of the Panopticon Tower, but against the automated defences set against them they could achieve little. Fortunately, other, more competent troops arrived at the scene: the elite Veletaris of the 905th Solar Auxilia Cohorts, the "Ash Scorpions".This elite formation raised from the Feral Worlders of Lethe successfully penetrated into the Panopticon Tower, clearing the way with Flamer sections, blasting CastellaxBattle-Automata apart with Rapier-tracked laser destroyers before reaching and valiantly charging the barrier of steel that stood between them and the control pulpit.Only a single Veletarii whose name wasn't even recorded succeeded in reaching the pulpit, sacrificing himself to shut down the blanketing signal that impeded Lord Admiral LaBray from taking control of the dire situation. Through its glorious sacrifice, the 905th Cohort has gained an undying glory that is remembered to this day.Finally able to join the Loyalist ships, Grand Admiral LaBray took overall command and promptly ordered the Dictatus-class Battleship Kurga to destroy the Panopticon lest the signal was somehow reactivated.Manoeuvring on its powerful thrusters, the Kurga made for the imposing spire, the ancient ram-battleship first seizing the Panopticon in its massive set of "jaws" before firing its thrusters at full power, ripping the Panopticon from Port Maw's surface.Soon battle raged in proximity of the Maw as Loyalists and Traitors slowly formed their lines of battle, but on the outskirts of the muster where the reinforcement squadrons from Numinal and Agathon lay, things were far different. The warships and refugee vessels at anchor had suffered distinctively few mutinies and were still shaking off the effects of the Traitor anathema signal.Puzzled, their captains were still trying to figure out what the commotion at Port Maw was about when almost unremarked one of the Cyclothrathine war-arks, the Arithmetic of Violence, powered her engines and began to move.The huge ship turned her prow towards the cruiser squadron hailing from the Agathean Domain, all staunch Loyalists. Without preamble, the colossal barrel-shaped war-ark silently broke apart, revealing row upon row of void torpedoes that ignited their plasma drives as one before racing towards the Agatheans.At such close quarters, there was nothing the brave crews and officers of Agathon could do. The torpedoes obliterated everything in their path, destroying smaller ships and Battlecruisers by the dozens -- leaving only the hence-famous Telemachus to fend for herself and start the arduous journey back home.With the squadrons from Numinal and Agathon destroyed, the flank was firmly secured for the Traitors, but the overall battle had reached a deadlock. Those ships that could still readily move had gathered into two battlelines facing each other.Neither had such numerical superiority so as to venture forth and force an engagement, both lines keeping out of range of each other and trying to keep Port Maw's mass and the hundreds of floating wrecks between them.It was then that an anomaly appeared on the Triumph of Reason’s radar screens: a faint echo return of an unknown fleet heading for the Maw, answering no hails and broadcasting no security codes.The echo returns were scrambled, somehow impeded by unknown means that were, however, known to be quite distinctive of Raven Guard vessels in stealth mode.Could it be that some survivors of the XIX Legion had come to Port Maw in its hour of need to help the beleaguered Loyalists? Unsure as to what position he should adopt, Grand Admiral LaBray proved cautious -- he correctly judged the twenty vessels now arcing for Port Maw to be hostile and decided not to let them reach the Traitor lines for it would tip the balance of power in favour of the Traitors.If, however, they proved to be loyal, they could join with his own fleet before launching a coordinated attack. Bound on an intercept course, the Grand Admiral realised too late that he had been led into a trap. The foremost vessels had indeed once been vessels of the Raven Guard, two modified Dagon-class Grand Cruisers, but behind them came the Vengeful Spirit, flagship of the Sons of Horus fleet carrying Horus himself onto the battlefield.Using the former Raven Guard vessels as ablative shields to soak up incoming fire, the Vengeful Spirit closed in on its powerful engines. Behind her were arrayed other Sons of Horus ships, forming a speartip whose point was the colossal Vengeful Spirit.Since their time as the Luna Wolves, the Sons of Horus had always valued the precision and utterly devastating effects of the decapitation strike -- a tactic they also adhered to in void battles. It was therefore no surprise that the Vengeful Spirit made directly for the Triumph of Reason at the heart of the Loyalist fleet.Smashing cleanly through escorting cruiser squadrons, the Vengeful Spirit launched a perilous manoeuvre that brought her directly above and alongside the flagship -- a manoeuvre no ship its size had any right to survive -- whilst the Triumph of Reason vainly attempted to roll and bring her broadside to bear.Almost at point-blank range the Vengeful Spirit released preciously rare tools of destruction -- Vortex missiles -- that ripped apart both the Triumph's Void Shields and outer hull before Dreadclaw and Kharbydis Drop Pods delivered Sons of Horus Breacher and Reaver Squads that fought their way through the bowels of the ship with consummate savagery.LaBray's own elite Lifeguard Cohort resisted where it could, concentrating around corridors and choke-points, their incoming fire potent enough to make even the vaunted Justaerin Terminators stop in their tracks, their Cataphractii Armour turning red and their casements running like hot wax.Casualties were horrifyingly high on both sides, but still the Sons of Horus pressed forward. On the Grand Admiral's order, mechanisms were thrown open and cryo-chambers vented, releasing hundreds of surgically augmented Ogryn Charonites into the corridors of the gargantuan ship.Hemmed by the narrowness of the Triumph of Reason's corridors, even the feared Astartes could not stand against these raging, foaming and bellowing monstrosities, their chemically and mechanically-augmented strength capable of ripping through bulkheads and power armour alike.The charge of the Charonites successfully disrupted the Sons of Horus' advance, each Charonite wreaking a heavy toll in blood before being finally brought down.For a moment the battle hung in balance, then the veil between realities parted and the Warmaster himself, Horus Lupercal, stood on the Triumph's deck. Hefting Worldbreaker, his immense Power Maul, the primarch led the counterattack, and against him even the chemically-induced fury of the Charonites could not stand.They did not back away, oblivious to the threat the Primarch presented, but were unmade by the Arch-Traitor's strength, their corpses flying apart or crumbling against adamantium walls.Realising all was lost, Grand Admiral Ospeus LaBray tried to escape from his bridge, making for the fighter bays of his immense flagship, but he perished in a devastating crossfire before reaching them.Whilst the Sons of Horus were set loose to massacre and defile as it pleased them, Horus broke into the Strategium of the Triumph of Reason and there addressed the Loyalist fleet: surrender now and enter his service as penitence for their ignorance and their lives would be spared, resist and only death would come for them.Thus began Horus' cruel reign of terror.