Netherrealms

The darkest recesses of existence pool in the gaps, chasms, and recesses between the known realms. They creep in and between the rest of existence like tendrils of rot finding purchase wherever it can, feeding off the residual energies of death and decay and storing it all in that festering, inscrutable pit at the bottom of the cosmos.
And yet, for as awful a reputation as these macabre realms have obtained, the gods have deemed it not only necessary but required for these places to exist, to maintain some concept of balance few can even attempt to truly understand.
-Thoughts of an Aumani Scribe

Just as Meliora is an amalgamation of the heavenly planes, the Netherrealms represent the seven Dark Realms: the Abyss, Acheron, Baator, Carceri, Pandemonium, and The Gray Wastes, not including the Negative Plane and what indescribable monstrosities lurk in its depths.
The Netherrealms are each and all connected by the River Styx, no matter where they come to lie in the drift of Wildspace. They have a habit of emerging wherever the Melioran realms aren't, and may even present themselves to mortals in local Realmspace (Material Plane) systems as "Dark Stars" to be worshipped and feared - as if that would prevent whatever grim fate they are likely soon to impart on whatever unfortunate things get caught in their orbit.

Type

Plane of Existence