Soul Grinders

When a Daemon’s physical body is slain, he can surrender his true name to the Forge of Souls. The dark bargain thus sealed, the Daemon’s crippled essence is bound to a mighty Warpmetal hulk. Thus is he reborn as a Soul Grinder.

Sometimes called Doomstriders, Harvesters of Souls, and Clinkerspawn, no two Soul Grinders are exactly the same, but all are bizarre to look upon. The transformation has a tendency to mimic the Daemon’s inner desires and then distort them just enough so that even it finds the results loathsome. Yet the change also grants might far beyond that which a Daemon normally enjoys. A Soul Grinder’s clanking tread shakes the ground with every step, and it is devilishly fast for a creature its size, able to scuttle swift as a horse’s gallop, or even faster should the scent of battle touch its nostrils. Piston-driven legs thud home with sickening force, crushing to bloody paste those beneath. Formidable though a Soul Grinder’s brute strength is, he does not need to rely on it alone to slaughter his foes, for the transformation grants weapons to match the newfound stature.

Legend tells that if the Soul Grinder can garner sufficient mortal souls, the Forge of Souls frees the Daemon from his mechanical prison and returns him to the existence he once knew. Alas, as with all bargains struck within the Realm of Chaos, this is a debt not easily settled. Many a Soul Grinder has come within a single kill of clearing his debt with the Forge of Souls, only to have ill-fortune see him destroyed, rather than the intended victim. Worse still, if vanquished, the Soul Grinder must sell itself to the Forge of Souls once again, or return to the oblivion it so dreads. Should a Daemon remain a Soul Grinder too long, his original identity begins to fade, subsumed into the machine that he serves. After a few millennia of the binding it is gone entirely. Thus can a Daemon come to be eternally damned, even as he seeks the same fate for mortals.

Source

 * Warhammer Armies: Daemons of Chaos (8th Edition) -- pg. 57