The Diasporex were a heresy the Great Crusade could not abide, not of the warp but of the flesh: humans and aliens sharing a single wandering civilisation, their fleets braided together across generations of exile. The Diasporex Campaign set the pitiless will of the Iron Hands against this coexistence, and the burning idealism of the Salamanders beside them, and the void ran red with the labour of their reckoning.
Ferrus Manus would not be denied. Where Vulkan counselled care for the human souls entangled among the xenos, the Gorgon saw only impurity to be excised, and the two primarchs strained against one another even as their Legions fought as one. The Diasporex were no easy prey; their ancient warships answered with weapons half-forgotten by the Imperium, and for long weeks the campaign hung in the balance of ambush and counter-ambush through drifting debris-fields.
In the end the fleet-culture was broken and scattered to the cold, its generations of memory extinguished in a single sustained slaughter. The Iron Hands counted it a purity restored; the Salamanders counted the human dead and said little. The friction between iron and flame did not end at Iydris, but it was here that the fracture first showed plainly, a hairline crack in a brotherhood the coming Heresy would shatter utterly.