Kelbor-Hal

Kelbor-Hal was Fabricator-General of Mars, supreme master of the Mechanicum and one of the most powerful beings in the Imperium: a lord whose word commanded forge-worlds beyond counting and armies of war-engines beyond number. Yet for all his power he nursed a deep and abiding resentment of Terra, for the Treaty of Olympus that bound Mars to the Imperium had also chained the priesthood's ambitions, and the Emperor had sealed away technologies and archives that Kelbor-Hal believed were the birthright of the Machine-God's faithful. That grievance festered across the long decades of the Great Crusade.

When Horus made his overtures, the Fabricator-General found in the Warmaster's rebellion the excuse he had long awaited. He cast Mars into treachery, threw open the forbidden vaults, and loosed the Dark Mechanicum upon those of his kind who would not follow, plunging the Red Planet into the fratricidal ruin remembered as the Schism of Mars. Under his rule the priesthood embraced the blasphemies it had once forsworn, and the forges that had armed the Imperium now armed its destroyers. Kelbor-Hal had traded his order's soul for freedom and vengeance, and the galaxy would burn the brighter for it.