Port Maw - Horus Heresy: When the Warmaster Horus revealed his ambition on the plains of Isstvan III, Port Maw was still under construction. It was, however, operable in limited fashion as a supply-point for those fleets that would eventually sail forth to confront the Renegade Warmaster and those Traitor Legions that had sided with him.The Port Maw Armada, however, would take no part in the following campaign. Under orders from Horus Lupercal -- then still believed to be the loyal Right Hand of the Emperor -- the Port Maw Exercitus had sent out much of its might to support distant warzones or on extensive and far-flung patrols, thus scattering most of its effectives across the sector and beyond.Some battlegroups had been temporarily reassigned to warzones and conflicts in other Segmenta, while some warships assigned to patrol were purposefully led into ambushes or distant corners of the galaxy never to be seen again.Port Maw would, however, be able to resupply some of the Loyalist Space Marine fleets that were sent to confront Horus, and both the fleets of the Iron Warriors and the Raven Guard stopped at Port Maw for a final resupply before sailing forth to what was to become the Drop Site Massacre.Both fleets received updated reports on Port Maw's status as well as new security codes clearing their advance. Deeming their routine codes and identification protocols unsafe, the Loyalist authorities had changed them and placed their own defences and troops at readiness, but all these measures were deemed as mere precautions. Nobody truly expected the Traitors to emerge victorious against the might of eight of the Emperor's Legions of Space Marines.In the closing days of 006.M31 news of the Drop Site Massacre finally reached Coronid Thule and caused a flare of panic amongst the ruling elites of the cluster.Having to rapidly reevaluate their situation, Loyalist Imperial Commanders soon found out that some worlds had already "gone dark," all communication lost and having likely been occupied or ravaged by the Traitors.The first real warning of impending doom, however, came not from the Cyclops Cluster or even the Grail Abyss, but Isstvan V itself. Isolated or in very small groups, ships hailing from the Isstvan System and belonging to the Shattered Legions -- the Raven Guard, the Iron Hands and the Salamanders -- found their way to Port Maw or other worlds such as Lascal and Dominica Minor, bearing with them the terrible news of their defeat.All these arriving vessels were battle-scarred, wounded and in some cases barely space-worthy, yet only the most damaged stayed in the Manachean Commonwealth or in the Cyclops Cluster -- nearly no Legiones Astartes chose to stay behind and fight the Traitors; most chose to retreat further after having accomplished emergency repairs or in some instances changed ship.Soon, however, the worlds of the Cyclops Cluster and the Manachean Commonwealth were girded for war. They found enemies already amongst them, lone outriders to the Warmaster's forces such as the dreaded voidship Ikon were sighted imposing Dark Compliances on ill-defended worlds, but most notoriously Mezoa. The mighty Forge World supplying Port Maw with much of its macro-ammunition was blockaded by unknown vessels and the entire fleet of its old rival from M'Pandex.Foreseeing a shortage of advanced munitions and macro-weaponry, the authorities at Port Maw were beginning to formulate a response to break through the blockade when dire news reached them from the edge of the Grail Abyss.Lascal, an Armada Imperialis High Anchorage with its own sizable fleet to defend it -- nearly forty ships-of-the-line and three Retribution-class Battleships, the Sceptre of Iron, the Ozymandias and the Star Tamer -- had been utterly destroyed.Their sole contribution to the war would be a garbled warning the astropaths had much trouble to decipher: the Death Guard Legion was heading for the Cyclops Cluster.Faced with this emerging threat, the Port Maw Armada could not commit its strength to aid the beleaguered world of Mezoa, nor would it risk an open battle for the ultimately non-strategic Grail Abyss. Reaching out for what ships of its own fleet it could, the Port Maw authorities tried to assemble its might to face the enemy, recalling every warship they made contact with while despatching a squadron of deep-range cruisers, the XVII "Sun Dragons", to investigate matters at Lascal.The Sun Dragons reported that the Lascal High Anchorage and the fleet that had been stationed there were now nothing more than a debris belt orbiting a murdered, ravaged and poisoned world.Solar Auxilia landing parties in full hazardous environment gear launched from the Sun Dragons' cruisers to the palace of Lascal's planetary governor and several known defence bunkers all returned, ashen-faced, with the same tale of utter destruction. The dead in their thousands covered the land, struck down in their stride by blistering airborne poisons and murderous nerve-agents.In those few places, such as the Imperial Governor's palace, which had been sealed in time, a more direct hand had been taken to destroy those huddled within. Ferrocrete walls had been shattered by direct cannon fire, bulkhead doors torn from their mountings by the merciless gauntlets of Power Fists, and everywhere was rank slaughter and the litter of spent bolt shell cases, unmistakably Legiones Astartes in pattern.As if any more evidence was needed of the perpetrators of this atrocity, in the auditorium of the Imperial Commander, above the cast-down Aquila and impaled in the bloated corpse of the man who had ruled there in the Emperor's stead, was a ragged banner bearing the death's head and black sunburst of Mortarion's Death Guard Legion -- a dire warning to those that would refuse to bow to the Warmaster Horus.As the Sun Dragon squadron left the charnel house of Lascal behind them, news of what they had found quickly spread, and in the star systems of the Cyclops Cluster, already fraying apart from each other in fear, pure terror now took hold.The "Murder of Lascal" as it soon was known, spurred defensive measures even further. The Cyclops Cluster and Manachean Commonwealth prepared for an inevitably bloody war. It was then that the cruel whim of fate intervened.