The domain created and managed by the Dingir Ereshkigal. It is a dreary sceneries that spread everywhere beyond the Dynamis, similar to ashen desert.
Souls of those who wore the mask and transformed into devil, as well as those who were killed by those devils are temporarily gathered in the Dark Realm. In addition, countless of so-called skeleton watchmen are wandering in there, souls hunted by the watchmen will vanish and reduced to the lifespan of devil that killed them. Nevertheless, majority of the watchmen has their function halted due to deterioration over the time, and the efficiency of soul adjustment is significantly lower compared with just after its construction. At the other day, the remaining ones were also annihilated by Mikado Kurosaki and Sera Kurashiki, and the Dark Realm became unable to accomplish its essential function.
"24 January 2019" addition
After receiving direct hit from the "Diabolic Beam" that was drawn from the ultimate power of Demon King Satan and guided by Mikado Kurosaki, the Dark Realm system itself collapsed. The souls of his sister—Kasuga Kurosaki and his sworn ally—Izumo Miyakonojo, as well as the vessel of Demon King Satan—Yamato Tennoji was released, and returned to their respective bodies. On the other hand, most of the souls that was sent to the Dark Realm prior to that point was already "processed" by the blade of gatekeepers that once existed in there, and there are no changes in the Diabolus who comes through the Black Point. From now on, its impact on a new person who wore the mask is unknown.
In addition, the fate of Mikado Kurosaki—who temporarily caught the ultimate power of Diabolic Beam with his own body, as well as Alexander cannot be confirmed, and they are still missing.