The Mechanicum of Mars

Before there was an Adeptus Mechanicus, there was the Mechanicum: the ancient priesthood of Mars, older than the Imperium itself and jealous of every secret it kept. When the Emperor set out to reunite the human race in the Great Crusade, He could not do it with soldiers alone. He needed the forges of the Red Planet, their war-engines, their star-ships and their limitless industry. The pact He struck with the machine-priests of Mars built the Imperium, and the day that pact shattered, it very nearly unmade it.

The Mechanicum worshipped not the Emperor but the Machine God, the deity they called the Omnissiah, whom they believed spoke through the cold logic and order of technology. Theirs was a civilisation of red-robed adepts who prized knowledge above flesh and machinery above men, and for all their loyalty to the Crusade, they never truly served Terra. They served Mars.

The Cult of the Machine God

At the heart of the Mechanicum lay the Cult Mechanicus, a faith that held all technology to be sacred and every machine, from a humble rifle to a towering war-engine, to house a spirit that must be respected and appeased. To repair a device was to pray; to master a lost science was an act of worship; and to let understanding slip away was the gravest of sins. Maintenance became ritual, conducted with incantation and sacred oils as much as with tools.

Above all, the priesthood pursued the recovery of humanity's lost golden age of technology, hoarding the fragmentary blueprints and forbidden knowledge of an era of genius that had long ago collapsed into ruin. The modern Adeptus Mechanicus inherited this creed almost unchanged, but in the age of the Crusade the Cult was wilder, prouder and far less bound to Imperial control. Its adepts held the human body to be a flawed and shameful thing, and replaced their flesh with augmetics until the most ancient magi were more machine than man, their minds swollen with data, their humanity all but shed.

The Red Planet and the Forge Worlds

Mars was a world-sized foundry, its surface an unbroken sprawl of manufactories, refineries and reactor-shrines that had armed humanity for thousands of years before the Emperor's coming. When He arrived at the Red Planet, He did not conquer it. He negotiated. The great compact between Terra and Mars recognised the Mechanicum as a sovereign power within the new Imperium, free to keep its faith and its secrets in exchange for arming the Crusade. It was a marriage of necessity, and beneath its surface ran a current of quiet mistrust that never fully drained away.

Mars did not stand alone. Across the conquered galaxy the Mechanicum established forge worlds, planets given over wholly to industry, each a smog-wreathed empire of foundries ruled by its own Fabricator and bound by the Cult's doctrines. From these worlds poured the endless munitions, war-plate and vehicles that the Crusade devoured. Whoever commanded the forge worlds commanded the means of humanity's survival, and the priesthood guarded that power with jealous care.

Ruling over all of it, in theory, was the Fabricator-General of Mars, the high priest of the Machine God and one of the most powerful individuals in the entire Imperium. In practice the forge worlds were a loose and fractious confederation, each a near-sovereign realm with its own traditions, hungers and rivalries, some hoarding knowledge others would have killed to possess. This proud independence had been the price of the Emperor's alliance, and it was the flaw through which treachery would one day worm its way into the heart of Mars.

Engines of the Great Crusade

The Mechanicum did not merely supply the war. It marched to war itself, and its armies were unlike any other in the Imperium. Ranks of cybernetic Skitarii soldiers, hard-wired for obedience, advanced beside lobotomised servitors built from human bodies to labour and kill without complaint. Grimmest of all were the battle-automata of the Legio Cybernetica, robotic war-constructs guided by cortex programming, able to tear apart infantry and armour with equal ease.

Mightier still were the two great orders the forges maintained. The god-engines of the Titan Legions, marshalled into the Legio Titanicus, towered over the battlefield like moving cathedrals, while the noble war-suits of the Knight Households added their feudal fury to a thousand campaigns. Only the Mechanicum could forge the heaviest weapons of the age, and only the Mechanicum truly understood them, a quiet leverage the priesthood held even over the Space Marine Legions, who depended utterly upon Mars for the tools of their trade.

The Schism of Mars

When the Horus Heresy engulfed the Imperium, the poison of that treachery reached the Red Planet. The Fabricator-General of Mars, seduced by promises of forbidden knowledge and freedom from Terra's restraints, threw in his lot with the Warmaster. What followed was a civil war within a civil war: the Schism of Mars, a planet-wide slaughter in which forge fought forge and priest murdered priest across the burning surface of the birthworld of the Cult.

Those who embraced the powers of the warp and the dark sciences the Emperor had forbidden became the Dark Mechanicum, unshackling horrors and daemon-engines that loyal adepts had spent lifetimes suppressing. The faithful Mechanicum, driven from much of their own homeworld, fought a doomed defence as Mars fell into ruin around them. When the fires guttered out, the Red Planet was a graveyard, and the priesthood was sundered in two: one half still sworn to the Imperium, the other loosed into damnation.

Legacy of the Red Priesthood

The Mechanicum survived the Heresy, but it did not survive unchanged. In the war's aftermath it was bound far more tightly to Terra and reborn as the Adeptus Mechanicus, formally a servant of the Imperium rather than an independent ally, its freedoms curbed and its oaths rewritten. Yet the Dark Mechanicum was never destroyed. Its heretek-priests still labour in the Eye of Terror and the lightless corners of the galaxy, forging blasphemous engines for the heirs of the Warmaster.

The schism that split Mars was never truly healed, only buried, like so much else of that terrible age, beneath ten thousand years of grim and watchful silence.