The Forge of Souls is a dark forge of the Ruinous Powers utilised to create malefic Daemon Engines as well as potent armaments and talismans to be used by the daemons in their eternal warfare. This forge lies beyond the dominions of mortals such as Warpsmiths of the Chaos Space Marines and the Dark Magi of the Dark Mechanicus.
The Forge of Souls exists entirely in the Beyond, deep within the Formless Wastes of the Realm of Chaos. This hellish forge is perpetually cloaked in a pall of black, oily fumes, rank with the acrid stench of forbidden metallurgy, dominated by a cacophony of strident grinding and the wailing of uncountable tortured spirits. This accursed place is where the blind, ever-mutating daemon forge-masters of Chaos eternally hammer at their creations in cyclopean smithies.
The black fires and infernal processes of these cavernous laboratories are fuelled by the souls of the damned and kept roaring by colossal screaming bellows, manned by legions of semi-sentient nightmare creatures. From the dark bowels of the Forge of Souls come all manner of hideous and unholy weapons. By means of the perverse technologies of the artisans of Chaos, daemonic energies are fused with arcane metals to create great jagged blades, weeping swords, barbed steel whips and other potent weapons and talismans, to be used by the daemons in their endless battles.
But as lethal as such weapons are, they are mere toys next to the greatest construct of the daemonic smiths. Amongst the most potent of these is the terrifying Daemon Engine known as the Soul Grinder, but countless other types, many entirely unique, exist. These terrifying creatures are the fusion of the most powerful of daemonic entities with machines of war that originate from outside the lmmaterium, but already have felt the touch of Chaos. These are often the wrecked remains of great Daemon Engines and other possessed vehicles, like the mighty Battle Titans of the Legio Mortis, or the rampaging Defilers created by the Traitor Legions. All this ruined materiel is absorbed into the Warp as the flotsam and jetsam of a galaxy at war, flowing from realspace into the Immaterium through the Eye of Terror, the Maelstrom and the other loci in the galaxy where different realities touch.
In the ash plains outside the Forge of Souls battle never stops, as many amongst the higher ranks of daemonhood vie with each other and duel for the chance of being the one to fuse with the mechanical constructs and become a Soul Grinder. This is because, unlike a possessed mortal body, these steel and ceramite shells can sustain a daemon in the mortal world for Terran decades, even centuries. During this time, the shape of each Soul Grinder will change, as their metal body slowly becomes more similar to the type of daemon possessing it.
Such a precious armoured form does not come for free. Great is the price that the artisans of the Forge invariably demand of each new Soul Grinder in return for the unholy incarnation. Before being released, the daemon must take the three Oaths of the Iron Pact with the Masters of the Forge. First, that all of the souls harvested by the great blades of the Soul Grinder will be used for the fuelling of the Forge. Second, that the wrecked remains of all of the war machines destroyed by the adamantium claws of the Soul Grinder will be offered to the Forge. Finally, and perhaps most significantly, that should one of the Chaos Gods attack the Forge of Souls and try to rule over it, all Soul Grinders will fight in its defence, discarding all of their previous loyalties to any of the four Great Powers of Chaos.
When a Dark Magus or Warpsmith enacts the rituals of summoning and calls upon the services of an incarnate Daemon Engine, it is likely that the source of the monstrosity is the Forge of Souls, and that every life the machine-daemon-thing reaps condemns yet another mortal spirit to an eternity within its searing furnace.
- Codex: Chaos Daemons (4th Edition), pg. 44
- Imperial Armour Volume Thirteen - War Machines of the Lost & The Damned by Andy Hoare with Alan Bligh & Neil Wylie, pg. 114
- White Dwarf Magazine #394 (UK), "New Releases," pp. 6-10