Forge of Souls

The Forge of Souls is a location found within the Realm of Chaos. When a Daemon’s physical body is slain, he can surrender his true name to the Forge. 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.

Legend tells that if said-Soul Grinder can garner sufficient mortal souls, the Forge 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.

Trivia
It is unclear whether the Forge of Souls is neutral territory between the Dark Gods, or solely controlled by Khorne, as the map layout of the Realm of Chaos situates the Forge directly within the Domain of the Blood God.

Source

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