Manachean Commonwealth - The Horus Heresy: As a vital and highly industrialised star system, it was clear that the Manachean Commonwealth would sooner or later come under the attack of the Renegade Warmaster Horus' troops. However, in contrast to the more fractious Cyclops Cluster, the worlds of the Manachean Commonwealth were both better protected and more powerful. On one hand, the proximity between the Manachea System and Port Maw meant that the military and naval might possessed by these two worlds would readily be able to support each other and thus posed a threat the Warmaster could not ignore. On the other hand, the industrial and repair facilities of the Port Maw installations constituted an ideal stepping stone for Horus' March on Terra. Where in the Cyclops Cluster Horus' armies had benefitted from the element of surprise, this would not be the case at Manachea or indeed Port Maw, as several Loyalist survivors, escapees from the Massacre of Istvaan V, had already spread word of Horus' victory. Worse yet for the Traitors, Port Maw was already rallying every available force to engage Horus' own war fleets. Fortunately for the Traitors, a large portion of its fleet was already engaged elsewhere in a protracted and bloody battle against an Ork Space Hulk designated as the Red Polyphemus. Other squadrons had also been despatched to far-flung sectors under the Warmaster's orders well before the Istvaan III Atrocity and were struggling to reach their home port when Horus struck simultaneously at Manachea and Port Maw. History has remembered these troubled times as the Manachean War, Horus having long since planned to weaken the Armada Imperialis battlegroups stationed at Port Maw. The Warmaster had initiated countless schemes and treacheries to ensure that when his axe fell, it would do so on a weakened and disoriented enemy. Horus' duplicity would culminate in the Treachery at Port Maw whose outcome would deliver nearly the entire sub-sector into his hands.Manachea's Planetary Governor, Lord Protector Pryamus Beket, died in the ruins of the Palace of Light among the slaughterhouse that had become his command amphitheatre. Defiant to his last breath, he stood before First Captain Ezekyle Abaddon of the Sons of Horus Traitor Legion after the murder of his city, which had taken six solar days to die. Holding his ground, the brave Lord Protector offered the towering Astartes only words of rebuke before being casually brought down, crushed by the powered claw of the Sons of Horus' First Captain as a normal man would swat aside a fly. With the terrible fate of Hive Illium to contemplate, the other hive cities of Manachea quickly surrendered. Manachea became the first truly autonomous domain over which flew the Eye of Horus instead of the Imperial Aquila. Yet Horus did not rule there, nor did the bleak Primarch of the Death Guard, Mortarion the Reaper. The Manachean Commonwealth fell under the sway of Taloc Thorne, a line captain of the Sons of Horus whom the Archtraitor had installed to rule in his absence. Claiming the title of Tyrant of Port Maw, Taloc Thorne would ensure that Manachea's industries and formidable workforce, but also the naval facilities at Port Maw, would now toil for the Warmaster. His seat of power was established in the blood-bedecked corridors and hall of the Triumph of Reason, Battlefleet Port Maw's former flagship, now aptly renamed The Lash. For it was under the cruel eye and whips of Horusite overseers that Manachea was now placed, the former proud and spectacular hive cities becoming little more than gigantic slave camps.Those that willingly allied themselves with the Traitors soon rose to power, ruling over their kin with iron fist and demonstrative cruelty. Taloc Thorne had been given his own company as well as six Cohorts of Solar Auxilia drawn from the infamous Cthonian Headhunters -- recruited on the Sons of Horus' homeworld of Cthonia but judged unsuitable for Astartes-conversion -- to maintain order in the Warmaster's new dominion. On more far-flung worlds, the authority of Horus could still be contested, and some planets like Mezoa or Numinal still actively resisted the invaders. Even though they were supported by the forces of the Imperial Knight Household of House Ærthegn and Forge World Cyclothrathe, the troops of the Tyrant were too few to police effectively such a vast domain as the Cyclops Cluster, the Grail Abyss and the Manachean Commonwealth together. Only in the Commonwealth was Taloc Thorne's power undisputed. However, with the advance of the Traitors' frontline, the Coronid Deeps became a separate warzone. Loyalist splinter-fleets and lone vessels of the Loyalist Legions shattered at Istvaan V remained a constant threat, while Mechanicum Cohorts of the Mezoan Mechanicum and Agathean Loyalists continuously harassed the domain and even dared to raid the worlds of the Commonwealth. Taloc Thorne's power, though substantial, was not enough to impose his will on forces that were supposedly his allies. The Wræken Dreor raided and plundered conquered worlds in the Grail Abyss while Archmagos Yelav Draykavac led the expansion of the Cyclothrathine Holdfast domain with his own war of conquest in the Coronid Reach Sub-sector.