Cyclothrathe was a former manufactory world known to the Imperium only by the most ancient texts, its name purged long ago by umbra-net data-phages by order of the highest possible authority. This minor Tertius Grade Forge World was located in the Coronid Deeps within the Segmentum Obscurus where it directly borders the Ultima Segmentum to the galactic East of the Cyclops Cluster. This Forge World was one of many worlds that were a part of the sovereign domain of the Mechanicum, known as the Cyclothrathine Holdfast, that had been founded within the devastated heartlands of the former Mitu Conglomerate. Although it could not rival the far more ancient neighboring Forge Worlds of M'Pandex and Mezoa in terms of industrial output, Cyclothrathe nevertheless vastly surpassed any traditional world's manufacturing capabilities.

The Cyclothrathine Mechanicum has always been an insular and aloof sect of the Mechanicum, even when it was still counted amongst those loyal to the Imperium of Man, few were those who readily trusted them. Born not of ancient history, but rather some of the darkest and most horrifying conflicts of the Great Crusade and long withdrawn into secret ways and the study of the arcane, they were recognised by their strange arachnid symbol and their robes not of traditional Martian crimson, but of deepest hearts-blood and sable, and by the fathomless storm-cloud hues which adorned their servants and engines of war. For years they had garnered a reputation for ruthlessness and aggression, both in defence of their domains from any xenos that crossed the frontier, and in pressing any claims they made to resource rights and territory. Imperial law and the intercession of Mars had been called upon on more than once occasion to keep Cyclothrathe's expansion in check. Bellicose and arrogant, the black-clad Magi of Cyclothrathe kept their distance even from others of their own kind, and where they walked, they walked alone.

During the Horus Heresy, the Warmaster Horus played on the jealousy and ambition of the Cyclothrathine Mechanicum to whom Mars was at best an unwanted and distant authority. The future would decide for this world an infamy seldom matched in the ranks of Forge Worlds. During these years, its name would become a byword for dark deeds and atrocity amongst the entire Imperium, as was its position within the Dark Mechanicum and the reputation of its dire Warlord, Archmagos Draykavac, cemented in the blood of countless planets. In the late 41st Millennium, it is many Inquisitors' beliefs that certain factions amongst their outcast kin in league with fallen Adepts of the Machine have recently re-established contact with the Traitors of Cyclothrathe, returned to threaten the northern marches of the Segmentum Solar as they did so many long millennia ago.


Cyclothrathe was a relatively young domain, founded long after the establishment of the nearby Forge Worlds of Mezoa or M'Pandex. Its origins could be found towards the end of the Great Crusade and the eradication of the xenos empire known as the Mitu Conglomerate. As a result, Cyclothrathe was situated amongst a devastated stretch of the galaxy, most worlds of the Mitu Conglomerate having been condemned to purge by Exterminatus; leaving an entire star system in ruins. Unsuitable for colonisation, these Dead Worlds, however, harbored precious alien technologies ripe for plunder and subsequent analysis. It was with this goal in mind that the Cyclothrathine Holdfast was created, its inception being somehow facilitated by the grievous damage sustained by the Mechanicum war-barque Cyclopean Mind. The Martian Magi crewing the Cyclopean Mind had realised their ship was too damaged to continue any further with the Imperial fleet and succeeded in landing their stricken ship safely on the planet's northern continent. From the wreck of the former Cyclopean Mind Forge World Cyclothrathe would arise; forge workings, bunker manufactories and lightning towers soon were raised in the skies or built deep underground to shield them from the baleful electromagnetic energies that wreathed the planet. Soon the Mechanicum outpost began its exploitation of the nearby worlds. Cyclothrathe's population would soon be swelled by those of the Explorator taskforces charged to scavenge the surrounding Dead Worlds of lore and relics who used it as a welcome base for their often dangerous expeditions. As more and more xenos relics were uncovered, some of them devastating weapon systems, Cyclothrathe soon developed its dual nature as outpost and Imperial weapon testing facility. Under patent from Mars, the ruling Synod of Cyclothrathe consisting of Magi of the Autokrator Order were charged to administer and build up the outpost into a full-fledged Forge World. Progress was, however, slow due both to the naturally occurring violent electromagnetic storms and the world's isolation from resupply or reinforcement. The former was somehow alleviated through the occupation of the nearby world of Arrian, whose mineral wealth was quickly put to the benefit of Cyclothrathe's industries.

Dawn of a New Age

By the closing years of the Great Crusade, Cyclothrathe had reached the status of a fully-fledged Tertius-II Grade Forge World but had encountered several difficulties along its rise; most notoriously it came under threat by unknown forces whose true nature has been since suppressed amid the data cores and archives of the Cyclothrathine and Martian Mechanicum. Although eventually vanquished, these foes considerably altered the Forge World's path, and Cyclothrathe became an isolationist, secretive and highly militant branch of the Mechanicum. Battle-hardened and bellicose, the Cyclothrathine Mechanicum all but severed its ties with the other worlds of the Coronid Deeps, including other Mechanicum possessions such as Mezoa and M'Pandex. Increasingly worried by this turn of events, immediately before the Horus Heresy broke out, the matter was brought to the attention of the Conclave of Mars by emissaries of the Mezoan Mechanicum. However, the matter seems to have been promptly dismissed by order of the Fabricator-General, Kelbor-Hal himself. Ever more bellicose and aggressive, Cyclothrathe's Magi had earned themselves a dire reputation for arrogance, hubris and secrecy who would pursue their own interest with selfish ruthlessness even if they were to spoil the ambitions of other worlds of the Coronid Deeps. On some occasions, even the Segmentum Court had had to be called upon to hold Cyclothrathe's desire and eagerness for expansion in check. By the dawn of the Horus Heresy it was obvious to all outsiders that Cyclothrathe followed its own agenda, at best acknowledging and bypassing the authorities of its neighboring systems, the Segmentum Court, the Martian Synod and the Imperium itself. The only real ties it upheld were with the worlds of the Manachean Commonwealth, trading convicts in their thousands in exchange for military equipment as to repurpose them into mining Servitors on Arrian where they would irremediably die in a few short solar months.  

The 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 himself, and through that alliance brought many Forge Worlds, Titan Legions and Magi into his sway, he 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 he 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 Istvaan, 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-kilometer 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.

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.


The majority of Cyclothrathe's Taghmata would, however, not partake in Horus' war against the Imperium but would instead lead their own war of conquest upon the neighboring star systems, the largely expanded ranks of its Taghmata permitting it to mount several offensives at once. It would be during this time that the infamous Archmagos Draykavac would rise to power and become more widely known. In theory the Taghmata Cyclothrathe served the Warmaster, but practically Horus' chosen representative, the Tyrant of Port Maw and Sons of Horus Captain Taloc Thorne, could exert little influence over the Mechanicum forces, leaving Draykavac to follow his own agenda. Cyclothrathe's expansion began with the conquest of the neighboring system of Olverach, a planet the ruling Synod of Cyclothrathe had long coveted. Following the Warp-routes the expansion quickly reached the Agri-world of Numinal from where it mounted an offensive on the two most important worlds of the Cerada System: the Civilised World of Cerada Prime and the mining colony of Cerada Secundus. The neighboring system of Quavausari was also quickly invaded. Most of these worlds quickly succumbed to the cohorts of robotic battle-automata that landed on their soil, but resistance was still fierce, notoriously on Cerada Secundus and Numinal where survivors of the Obed Cohorts of the Solar Auxilia still fought on. Following severe losses at the Liberation of Numinal, Cyclothrathe's expansion lost its initial momentum, the emergence of the new threat constituted by the Agathean Cohorts forcing Draykavac to consolidate his latest conquests.


The Cyclothrathine Mechanicum is a highly secretive branch of the Adeptus Mechanicus and is as such extremely isolationist and wary of outsiders. Little is known of its inhabitants or indeed how far their organisation differs from the more standard pattern of the Adeptus Mechanicus. What is known is that Cyclothrathe is ruled by a synod of Archmagi as tradition demands and that it maintained a sizeable Taghmata vastly superior to any other known Tertius Grade Forge World to protect its own possession on Arrian. Cyclothrathe's isolation has further led to the development of several idiosyncrasies that considerably diverge from the Martian canon, which included their own writing and the marked preference of dark-blood and sable-hued robes over the more traditional crimson of the Mechanicum.  


  • Cyclothrathe – Cyclothrathe is a rocky, barely life-sustaining world wracked by violent electromagnetic storms which may indeed be the reason why the planet was never colonised by the xenos races of the Mitu Conglomerate. With the homeworlds of this xenos empire in the region devastated by Exterminatus-class weaponry and rendered uninhabitable, Cyclothrathe's worth as a habitable world rose exponentially. The planet itself mainly consists of broken plains of black granite -- vestiges of its former volcanic state -- which proved highly stable. Not unlike the ecosystem of Vraks Prime, Cyclothrathe's seas are highly sulfurous, which results in devastating electromagnetic storms. Still rich in minerals due to its lack of colonisation, Cyclothrathe would rapidly become a productive Forge World and the beating heart of the Cyclothrathine Holdfast.
  • Arrian – Where Cyclothrathe makes for a harsh place to live, Arrian is far deadlier. Arrian is a sulphurous, poisoned world with an atmosphere thick with chlorine gas, and therefore utterly inimical to human life. Rich in minerals and easily accessible chemical deposits, large-scale mining and extraction facilities had been rapidly constructed across the world's surface to meet the industrial needs of Cyclothrathe, of which Arrian was a directly-administered possession. Lacking a native population, Arrian's miners were directly imported by the Magi of Cyclothrathe, their hellish existence made possible only by extensive augmetic adaptation, despite which mortality rates were disastrously high. For many years, the demand for new labour was met by treaty arrangement between Cyclothrathe and the distant worlds of the Manachean Commonwealth, trading convicts by the thousand in return for arms and other advanced products of Cyclothrathe's forges. During the onset of the Horus Heresy, however, with Cyclothrathe's growing isolation, this agreement had been allowed to lapse and how the presumed shortfall in labour was replaced remains unknown. Arrian is also the home of the Knight House of House Atrax, which has since the Heresy been reduced to little better than a thrall-house by the powerful Cyclothrathine Mechanicum.

Notable Campaigns

  • Treachery at Port Maw (008.M31) – Secretly in league with Horus, the Cyclothrathine warships join the grand muster of the Imperial Armada at Port Maw. Following the first attack wave and the confusion caused by the perfidious scrap-code attack, the Cyclothrathine war-arks open fire at close quarter against Loyalist ships. One of them, the Arithmetic of Violence annihilates nearly the entire cruiser squadron of Battlefleet Agathon, leaving only the Telemachus to fight on and ultimately escape.
  • The Liberation of Numinal (009.M31) – Conquered in the last days of 008.M31 and since occupied by Mechanicum forces, Numinal would become the first real defeat Cyclothrathe and Archmagos Draykavac would suffer. Having been forced beforehand by civil unrest to leave the conquest of Cerada Secundus to one of his subordinates, Draykavac voyaged to Numinal to ensure his plans are carried out: the forcible conversion of Numinal's civilian population into Servitors and Adsecularis troops. Draykavac was still on Numinal when the Agathean counterattack, led by the famed Ireton MaSade, struck. With his own Battleship, the Sacra Astra forced to retreat, Yelav Draykavac was stranded on-world and took steps to repulse the Loyalist attack. His forces had, however, been overseeing the processing of Numinal's population and needed time to assemble, which gave the Loyalists the opportunity and time needed to considerably fortify their landing zones. Loathe to interrupt the processing, Draykavac ordered his Knights and personal retinue to protect the massive amphibious crawlers that had been commissioned for this task and dispatched a token force to conduct reconnaissance on this new and unknown enemy. Soon Draykavac discovered that he would face Agathean Cohorts of Solar Auxilia bearing the livery of the long-decommissioned 60th Expeditionary Fleet. Expecting enemy reinforcements, Draykavac reinforced his own attack wave en route. Their task would be to keep the Agatheans under pressure as to give him time to amass a larger secondary force to crush the Agathean beachhead. This first attack wave would suffer far heavier casualties than he expected, Ireton MaSade having issued blast-charger capacitors to his troops which could readily damage the Castellax-class Battle Automata usually impervious to small-arms fire. The Cyclothrathine forces grudgingly retreated, the lesser Magi unwilling to assault such a heavily defended position and risk their lives doing so. Seizing the opportunity, several insurrections arose on Numinal, threatening the overall success of Draykavac's plans. Draykavac had no other choice but to personally lead the next attack which would include his entire retinue of Thrall-Knights, the Agatheans displaying a considerable lack of armor which could be exploited. Little did he know that this was specifically what Ireton MaSade had gambled on. On his command, his own Knight detachment -- compromising a great deal of House Orhlacc as well as several House Ærthegn renegades and even some Knights of House Hermetika -- deployed using antique Khobol-class heavy assault landers. Outflanked, Draykavac has to redeploy his own Knights as a bodyguard to protect himself. While the Knights fought each other, the Solar Auxilia surged forward from their defensive lines and pressed back the Mechanicum forces. Realising that he himself was the enemy commander's objective, Draykavac ordered his bodyguard to form up on him and cover his retreat, sacrificing his troops so that he might live. Fleeing from the battlefield, Draykavac succeeded in reaching his command compound from where he made good his escape into orbit. His own life had been preserved, but Cyclothrathe had lost definite control over Numinal.
  • Raid on Cerada Secundus (009.M31) - Four solar weeks after the successful Liberation of Numinal, the Agathean fleet attacked the vessels of Forge World Cyclothrathe supporting the conquest of Cerada Secundus. This time the Agatheans would not prove victorious, the combined firepower of the Mechanicum warships forcing them to retreat under heavy losses.   
  • The Genocide of Goth (Unknown Date.M31)   
  • The Lucine Travesty (Unknown Date.M31)   
  • The Death of the Donia League (Unknown Date.M31)   

Notable Cyclothrathine Personnel

Archmagos Draykavac

Ancient Remembrancer sketch of the infamous Archmagos Yelav Draykavac

  • Archmagos Yelav Draykavac - Though he would become one of the most reviled servants of the Dark Mechanicum, Archmagos Yelav Draykavac was an all but unknown figure before the galactic civil war of the Horus Heresy sundered the Imperium. This bestially-masked and black-robed Magos served as the chief military emissary of the Forge World of Cyclothrathe and the foremost field commander of its Taghmata, answerable only to the sinister and hidden tribunal which ruled his lightning-wracked world. As part of Draykavac's command, he also held the rank of Sovereign-Prelate of the Thrall-Knight House of Atrax, which was fully oath-bound to Cyclothrathe which, while nominally it still had its own seneschals and master, was in reality little more than a puppet of the utterly callous and inhuman Archmagos Draykavac. With the outbreak of war within the Coronid Deeps, Draykavac was at the forefront of the campaign of invasion and conquest Cyclothrathre carried out in the name of the Traitors, swiftly amassing a tally of atrocities and massacres to his name that set him apart as one of the most hated of his kind. Declared Heretek Ultima by the Great Synod of Martian Unification, and held responsible for, among other atrocities, the Genocide of Goth, the Lucine Travesty and the death of the seventeen worlds of the Donia League, his long war would extend far into the Great Scouring and beyond. His ultimate fate has yet to be ascertained, though his warship the Sacra Astra 's abandoned hulk was discovered adrift in the Maelstrom. In its encrypted data-archive was found much of the extant knowledge of the Dark Mechanicum now possessed by the Adeptus Terra. This dark archive contained many unexpurgated strategic reports, personal analyses and djinn-data from Draykavac's many battles, including a detailed account of the counter-invasion of the Agri-world of Numinal.

Cyclothrathe Appearance

Even before the outbreak of the Horus Heresy and the birth of the Dark Mechanicum the Magi of Cyclothrathe had considerably distanced themselves from the Martian canon. In general they favored robes of darker hue than the far more common Mechanicum crimson, colours such as black and dark crimson seemingly enjoying the favour of Cyclothrathe's population. Perhaps as a by-appearance of their Forge World's early struggles, they disdained the use of precious metals such as gold or silver in purely artistic or decorative matters, preferring naked steel or more sombre alloys such as sombre brass, which gave them a most sinister appearance. The bellicose nature of this particular branch of the Mechanicum also included the application of killing marks on esteemed or particularly successful robotic battle-automata, a tradition that seems to have been well-established before the dire events of 008.M31. Even at the very beginning of Cyclothrathe's expansion within the Coronid Reach, reports show numerous kill-signs on several battle-automata, although against which enemy or even race of xenos these were earned remain a complete mystery.

Cyclothrathe Heraldry

Cyclothrathe Mechanicum Icon

Cyclothrathe Forge World Icon

The most prominent element of Cyclothrathine heraldry was the common arachnid-glyphs they took as their emblem. Usually rendered in crimson on a field of black -- though sometimes inverted -- this glyph strongly resembles an iconic representation of a spider, its "legs" being rendered as lightning-bolts and the entire emblem being set in an encompassing crimson cog. Due to their submission to the Cyclothratine Mechanicum, it was most common for the Thrall-Knights of House Atrax to field the arachnid-glyph of Cyclothrathe, the emblem of the Forge World placed surmounting the personal arms of the scions to indicate the primacy of Forge over House. The Thrall-Knights' upper dorsal plating would also bear the mark of the Sidon Protocols, though House Atrax suffered under a particularly harsh interpretation of this pact.

Notable Vessels

  • Arithmetic of Violence – Mechanicum War-Ark. The Arithmetic of Violence was involved in the infamous Treachery at Port Maw, firing its entire complement of Plasma Torpedoes in one devastating volley against the gathered vessels of Numinal and Agathon that had followed the Imperial mustering call. All save the Telemachus would perish under this devastating assault. 
  • Sacra Astra – Mechanicum War-Ark. Command-vessel of the infamous Archmagos Draykavac which would serve him during the entire span of the Horus Heresy and the Great Scouring. Initially damaged during the naval battle prior to the Liberation of Numinal, the Sacra Astra would quickly be repaired and would continue to plague the Imperium for decades to come. The abandoned hulk of the Sacra Astra would eventually be found adrift in the region of the Maelstrom, its surviving data-cores and archives -- communally designated as the Draykavac Archive -- representing much of the knowledge gathered by the Adeptus Terra on the Dark Mechanicum.


  • Imperial Armour Volume Thirteen - War Machines of the Lost & The Damned, pg. 13
  • The Horus Heresy - Book Four: Conquest by Alan Bligh, pp. 40, 55-63, 76-77, 300
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