The Rise of the Dark Mechanicum is one of the most pivotal and sinister events in the Horus Heresy, marking the split of the Mechanicum into its loyalist and traitor factions. As the Galactic Civil War divided the Imperium, many forge worlds were ripe for rebellion, disillusioned with the Emperor’s tight control over their ancient and secretive operations. The Mechanicum‘s autonomy and distrust of the Imperium provided fertile ground for Warmaster Horus to sway key figures to his side, igniting the fires of treachery across Mars and beyond.
The Seeds of Rebellion
Magister-Lictanex Regulus, envoy of the Mechanicum to Horus, made the critical move of infiltrating Mars with a delegation of Iron Hands loyal to the Warmaster. Their mission: to meet with Fabricator-General Kelbor-Hal, the head of Mars, and secure his allegiance by offering a dangerous prize—the Vaults of Moravec. These forbidden vaults, sealed by the Emperor himself, held dark and ancient technologies that even the Mechanicum dared not explore. Unlocking these vaults not only provided Horus’ forces with dangerous knowledge but also unleashed a malevolent plague that would devastate the Mechanicum’s loyalist forces.
The Death of Innocence
When Kelbor-Hal opened the Vaults of Moravec, he unleashed a virulent plague of scrap-code—a corrupted, malicious digital virus. This code spread through the systems of Mars like wildfire, disabling vital infrastructure and causing massive system failures, from reactor meltdowns to life support collapses. This catastrophic event became known as the Death of Innocence, a tragedy that claimed millions of lives and threw loyalist forge worlds into chaos.
While military systems were shielded long enough to protect them from total devastation, the scrap-code turned those loyal to Kelbor-Hal into brutal, mindless instruments of war. As their morality was stripped away, the seeds of the Dark Mechanicum were sown. These corrupted tech-magi delved into forbidden knowledge, creating terrifying machines and unleashing legions of Stalkers—twisted abominations designed to crush the loyalist Mechanicum.
The Fall of Magma City
One of the first and most significant battles in this war was the Siege of Magma City. Despite being mostly spared by the scrap-code due to a new noospheric defense network, the city became a focal point of the Dark Mechanicum’s wrath. The Knight Households of Taranis and the Legio Tempestus rushed to defend it, but the corrupted forces of the Dark Mechanicum were relentless.
The Rise of the Dark Mechanicum expansion book for Legions Imperialis allows players to experience this pivotal moment in the Horus Heresy. The Escalation Campaign format steadily increases in points as battles grow in scale, culminating in a grand clash where players can recreate the final, desperate defense of Magma City.
The expansion captures the tragic downfall of the Mechanicum, turning once-loyal defenders of the Imperium into the corrupted Dark Mechanicum forces, who would go on to plague humanity throughout the Horus Heresy and beyond. This dark chapter in the Imperium’s history marks the birth of a faction whose hunger for forbidden knowledge and unshackled technological experimentation continues to pose a grave threat to the galaxy.
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