Red Butchers

The Red Butchers were a specialised shock-assault unit of the World Eaters Legion during the Horus Heresy. They psycho-sugery inflicted upon the Butchers of the so-called Butcher's Nails hammered into their skulls and the awakening taint within the World Eaters Legions combined to create a superhuman killing machine without reason or restraint, controlled only through the use of brutal shock implants and the prison of their specially constructed Terminator Armour into which they had been fused by the Legion's Techmarines. In between battles they were hung in chains in the holds of the World Eaters' warships, foaming and screaming in impotent rage, until such time that they were released once again against the Loyalist forces of the Imperium or upon the innocent.

History
In the opening days of the Horus Heresy the Istvaan III Atrocity unleashed a madness that had long festered in the World Eaters Legion and its Primarch Angron, a blood-hungry rage that afflicted the very core of the Legion's being and was amplified by the horrific hyper-aggression-inducing cranial surgery and the implantation of the Butcher's Nails into their skulls, that many World Eaters had subjected themselves to. On the killing ground of Istvaan III, there were World Eaters on either side of the conflict who succumbed utterly, devolving into mindless frenzied savages that could not be controlled. Rather than "putting down" such individuals as had happened in the past (as such things had occurred from time-to-time long before the Horus Heresy), the Apothecaries had the mad subdued and chained for a far darker fate.

The Techmarines made customised Terminator suits from recovered wargear for them, fashioning them as both armour and as confinement; mechanised prison cells that could be immobilised with a remote signal. Hung in chains in the holds of the World Eaters' warships, foaming and screaming in impotent rage, the Red Butchers were born. Unleashed first against the Loyalists at Istvaan V, these damned souls, insane with wrath were loosed to careen blindly into the foe, hacking and slaughtering with savage abandon. Few survived, but the fragments of their Terminator suits, spattered with gore, were found and remade anew for fresh occupants to inhabit.