Ordo Reductor

The Ordo Reductor is a specialised military division of the Adeptus Mechanicus that makes use of the forbidden weapons of a bygone age, engaging primarily in siege warfare.

History
Little is known of the origins of the Ordo Reductor faction of the Mechanicum, but presumably it hails back to the formation of the Mechanicum during the Age of Strife. The Ordo Reductor were primarily siege specialists and had access to many archeotech devices and forbidden technology. Following the success of the Unification Wars on Terra, the Emperor of Mankind sought a negotiated alliance with the Mechanicum Parliament that ruled over Mars. In return for supplying materials for his armies and building a mighty war fleet for his crusade to the stars, the Emperor promised to protect the Tech-priests and respect the sovereignty of their Forge Worlds. Mars consented to the alliance with Terra, and  signed the agreement known as the Treaty of Mars, or the Treaty of Olympus Mons within the Mechanicum. The Cult Mechanicum officially became the Adeptus Mechanicus of the new-forged Imperium of Man. The Tech-priests of Mars lent their arts and their formidable forces to the cause of the Emperor's Great Crusade, sending out numerous different factions of the Mechanicus to serve with the Imperial Expeditionary Fleets, such as the Collegia Titanica, Skitarii, Legio Cybernetica, Centurio Ordinatus and the Ordo Reductor. These forces would prove instrumental in the expansion and the forging of the Emperor's burgeoning Imperium to reunite the disparate tribes of humanity.

Forces of the Ordo Reductor

 * Mechanicum Thallax Cohort (Thallaxii) - During the Great Crusade and Horus Heresy eras in the late 30th and early 31st Millennia, the Ordo Reductor possessed a faction of heavily augmented cyborg shock-troops known as the Thallax Cohort. The Thallaxii differed from the standard Skitarii regiments both in their purpose and the unique degree of their augmetics. The Thallaxi Centuries utilised a divergent form of Power Armour technology known as the Lorica Thallax, which, unlike that used by its Space Marine counterparts, was permanently, surgically bonded to the body of the wearer. The Lorica encloses the major organs, nervous system and cerebrum, but entirely replaces the skeletal structure and limbs with armoured bionics powered by an internal reactor-core. Surgical excision of the subject's pain sensors, emotions, and normal human sensory apparatus and the agony caused by the Lorica 's implantation, leaves the Thallax a cold, calculating killing machine (albeit one that retains a degree of independent thought). To some amongst the Mechanicum, this operation skirted the edge of abomination, yet the baleful Ordo Reductor continued Thallax conversion regardless; using suitable Forge Guard, fallen Skitarii, and other subjects obtained from more mysterious sources. It is not known if the Ordo Reductor still possesses the archaic technology used to create Thallaxii troops in the present era of the late 41st Millennium.

Known Vehicles

 * Land Raider Achilles - The Land Raider Achilles originated in the closing years of the Great Crusade. The Achilles Pattern is perhaps the rarest and most venerable Land Raider variant still used on the battlefields of the late 41st Millenium. It was originally created by the Imperial Fists Legion in response to a dire xenos threat now lost to the mists of history, and is fittingly rare outside the armouries of the Imperial Fists, their Successor Chapters and the Ordo Reductor of the Adeptus Mechanicus.
 * Siege Wrecker - A Siege Wrecker is a general term given to a specialised form of massive close combat weapon intended for use by Mechanicum battle-automata which are utilised by the Ordo Reductor. Wreckers are designed to enable these heavy assault units to smash through fortifications and easily crush armoured barricades and defences in siege warfare. The most common form of this weapon is a hydraulic ram or massive disruption-field augmented hammer, although specialised forms of heavy claw or drill systems are also used.

Notable Campaigns

 * Istvaan III Atrocity (Unknown Date.M31) - Units of the Ordo Reductor under Magos Calleb Decima were among the few Loyalist survivors of the Istvaan III Atrocity that marked the beginning of the Horus Heresy.
 * Achilus Crusade (ca.777.M41) - At the outset of the Achilus Crusade to reclaim the Jericho Reach located in the outer reaches of the Segmentum Ultima for the Imperium, the Ordo Reductor sent two Siege Formations as a part of the supporting contingents supplied by the Adeptus Mechanicus for the Crusade.
 * 13th Black Crusade (999.M41) - When Abaddon the Despoiler and his Forces of Chaos assaulted the Fortress World of Cadia during the 13th Black Crusade in 999.M41, the Ordo Reductor aided in the defence of that beleaguered Imperial Fortress World by providing a Demi-Legion of their coveted war engines.

Heraldic Devices of the Ordo Reductor
The various arms, sects, cults and factions of the Mechanicum commonly displays heraldry of a widely varying degrees. To outsiders a great deal of the nuance, symbolism and application of these signifiers is lost, shrouded by the arcane doctrines and circles of the Cult of the Omnissiah's worship, but the broadcast and most general interpretations are widely understood. In many such sects of the Mechanicum, the deep crimson livery most associated with the Machine Cult is in fact reserved most often for its sworn and initiated priesthood: the Magos, ordained Enginseers, logisters, autosavants and so on, and by lessening degree their initiates and close retainers. The bulk of their soldiery, however, as well as their laymen servants are usually clad in darker hue, often of a livery associated with their Forge World or particular order, but marked always with the heraldic device of their masters.

Such is the common case with the Thallax. Where in service with the Ordo Reductor directly, it is common for the Thallax's armour and limbs to be over-plated with either burnished steel, polished bronze or, more rarely, gold or some environmentally protective coating. This is further adorned with colouration and iconography marked upon one or both pauldrons and/or more rarely the breastplate featuring the heraldry of their order of service, cohort designation, Forge Stamp and issue. During the Great Crusade and early Horus Heresy era, where the Ordo Reductor unit had been embedded for a time of service with a particular Space Marine Legion Rogue Trader Militant, Titan Legion or Imperial Army Battlegroup, it was often customary to adopt in part the heraldry of that larger formation, and often for the Broken Tower emblem of the Ordo Reductor to be heraldically parted with the symbol of the principal affiliation, as shown with the following examples: Top Row (from Left-to-Right):
 * Ordo Reductor/Iron Hands Legion; Sicronus-Septus Cohort
 * Ordo Reductor/Sons of Horus Legion; Steel Wolves Cohort

Bottom Row (from Left-to-Right):
 * Ordo Reductor/Word Bearers Legion; Gravis Logos-Nul Cohort
 * Ordo Reductor Phaeton Sigma-5-Osedax Cohort