The Shadow Realm.
Originally, this realm had been so close to the Shadow Plane that its interior had been assimilated into a half-shadow state, and everything was gray. Most of the petitioners within the realm were shadow creatures as well. But after Soren took control of it, everything inside had been reconstructed. In particular, the once gray, hazy world now had some color. However, the realm was enormous, and without entering it in his true body, Soren could not complete the transformation. Thus, its northwestern region remained a desolate realm of shadows.
However...
Some unusual changes had taken place here.
An enormous Pool of Reincarnation had been installed here. Petitioners could neither become pregnant nor reproduce, even though the Gods granted them lifespans far beyond those of mortals, sometimes exceeding a thousand years.
But!
No petitioner could become pregnant or reproduce. Even outsider servants could only be created in angelic form. Thus, the population of a God's Realm could not increase from within; it could only rely on souls from other worlds. This was also why, when certain deities' churches on the Material Plane were destroyed, their realms quickly withered or even collapsed outright.
Squads of heroic spirits guarded the border.
A river marked the boundary of this land. When Soren used his powerful divine power to tear open space and draw water of the River Styx into his realm, the special Pool of Reincarnation already installed here began to operate.
Soren could not simply transform souls into his own petitioners.
However, he could transform those souls into other forms. Demons were only one possible form a soul could evolve into.
Once the water of the River Styx carried souls into Soren's realm, the Pool of Reincarnation began operating automatically under the influence of planar laws. Then a shadow appeared