Cyclothrathe - Horus Heresy: It is not known how the jealousy and ambition of the Cyclothrathine Mechanicum came to the attention of the Warmaster Horus, but it was so, and it may even perhaps have formed part of a larger strategy in dealing with the Mechanicum as an ally in revolt, and perhaps one day as a future enemy. For a while, Horus had courted and indeed caused the corruption of much of the Martian Mechanicum, and the Fabricator-General Kelbor-Hal himself, and through that alliance brought many Forge Worlds, Titan Legions and magi under his sway.Horus had also courted a number of Forge Worlds and archmagi to whom Mars was at best an unwanted and distant authority. This was, for instance, the case with Sarum and with Esteban III, both Forge Worlds whose loyalty secured for Horus lines of supply which did not depend on the writ of Mars, and with minor Forge Worlds such as Cyclothrathe, whose industrial resources were not of such magnitude, but brought other, more unique powers into the Traitors' fold.In return Horus offered freedom; no ultimate master but himself as a disinterested overlord who did not care to interfere with their work, their creed or where their arts led them so long as his rule remained unopposed and his warriors were glutted with arms. To Cyclothrathe it seems, long before blood was shed at Isstvan III, Horus offered something else as well: an empire, a domain to rule as their own in his name. For years Cyclothrathe's vault-fanes and sunken forges had labored in secret and without the knowledge of either the Imperium nor Mars; fashioning baroque engines of destruction and unliving legions of robotic Battle-Automata, stockpiling them in the deep vaults beneath their lightning-scoured world, waiting for the trumpet blast of war to call them forth.Perhaps more so than other turncoat forces, the Cyclothrathine Mechanicum bid its time well. Having used the years prior to the Horus Heresy to massively build-up the forces of its Taghmata, the Forge World commanded a force far greater than those readily at the disposal of a Tertius II Grade Mechanicum world.Despite their military strength, the magi did not readily engage in a war of conquest as soon as Horus' treachery became general knowledge but became even more reclusive. This had naturally only been a ruse, so that following the fall of the Cyclops Cluster, when Grand Admiral LaBray issued his rallying call, Cyclothrathe would be counted among the Loyalist forces.Cyclothrathe's involvement in the galactic civil war began with the Treachery at Port Maw. The Cyclothrathine Mechanicum had dispatched three of its mightiest vessels to the Imperial mustering at Port Maw, amongst them the Arithmetic of Violence, a gigantic five-kilometre long war-ark whose flanks swarmed with void-automata. The storm-grey vessels of Cyclothrathe were readily welcomed at Port Maw, being seemingly the only Mechanicum-bound forces still on the side of the Imperium now that Mezoa was blockaded and M'Pandex had turned Traitor.As the events of the Treachery unfolded, the Mechanicum war-arks would carefully avoid combat, using the confusion to maneuver themselves into an ideal position to launch a sudden and overwhelming attack against the warships of Battlefleet Agathon and the sleek pirate-killers from the Cerada System. Taken totally by surprise one lone vessel would survive, the Agathean cruiser Telemachus which would carry news of this new treachery to its distant homeworld at Agathon.With the most serious threat neutralised and Port Maw in the hands of the Traitors, Cyclotrathe would then assist the Sons of Horus in their conquest of the Manachean Commonwealth, using the proximity of its homeworld to despatch Taghmata forces to seize and capture the astropathic relay on the world of Vlorath Srader. As per agreement, Cyclothrathe would then cede a sizable portion of its military might to serve directly under the Warmaster.