A few Daemon Worlds are dominated by the remnants of the Dark Mechanicus that once followed Horus. These Dark Mechanicus Forge Worlds are wholly given over to daemon-machines and infernal industries, where mills grind flesh and suffering is the currency used to make the insane visions of their nightmarish masters real. Countless millions are enslaved to work in a world-spanning network of labyrinthine forges, churning out an endless supply of weapons and armaments for the Traitor Legions' Long War against the Imperium. The masters of these Dark Mechanicus Forge Worlds, most now half-daemonic machines themselves, have long since left the shreds of their humanity behind and are beholden to none -- be they mortal or Chaos God. They sell or barter their unholy inventions and arms to the highest bidder, be they warlord, demagogue, Chaos Sorcerer or Daemon Prince without favour, and their coin of exchange is always the same -- new raw materials -- the flesh and souls of slaves for the Dark Forge World's unquenchable hunger.
The notorious Heretek Illucis Grizvaldi and his Heretek cult followers are known to prey upon Imperial fears in regards to the immortal soul and its possible destruction. They do so by heavy-handed use of Oblivion Volitors. These devices are a corrupted and clumsy pattern of neuroaugmetic; when surgically implanted into the brain, an Oblivion Volitor turns a man into a soulless "Obliviate." Obliviates are empty shells, living on after the soul is consigned to nothingness. Hereteks further augment Obliviates with crudely implanted blades and metal fangs, so as to use them like attack animals. They debase the divine form of Mankind by whipping Obliviate packs to savage their foes. But the true weapon is terror -- terror of oblivion brought to cherished souls, terror that the God-Emperor’s protection is sundered. To the perception of a psyker, there is little difference between an Obliviate and an aggressive Combat Servitor. Illucis Grizvaldi held court for his Heretek vermin upon the world of Scintilla at the opening of the 8th century of M41. Newly made Obliviates were leashed and naked -- bloody, drooling, and empty-eyed. The idea that those torn souls would never feel the God-Emperor’s embrace put terror into Imperial hearts. The Arch-Heretek had destroyed for all to see the essence of the faithful by means of the heavy, clacking augmetics embedded in their skulls. It was through such tools of fear and death that Illucis Grizvaldi held sway over his underhive domain on Scintilla before the Inquisition forced him to flee. Grizvaldi still remains at large to this day, his current whereabouts unknown.