The Hollow

The skin of the universe. A strange shadowy realm that exists outside the universe. Strange creature dwell here. The Ilazhim were banished here millennia ago by the Ehoshim, where they sleep and dream. There are many strange beings here and it is often uncertain if they are just figments of the dreams of the Ilazhim.
It is very difficult to enter the Hollow (and even harder to escape), but occasionally dreamers can be lured into crossing over into the Hollow, and become prey for the inhabitants. Shaman seem to be able to step in and out of the Hollow at will and can even bring other dreamers into the Hollow, though a Shaman will always make sure to be wearing their surreal animal masks when the are here.
Another group who are able to enter are the assassins of the Shadow Clans, Clan Chareda & Clan Zhayada have created a rather foul tasting potion, Oyuda, which enables them to step briefly into the Hollow, which functions like a "teleport" in the normal world. They "step/transition" into the Hollow, take a couple of steps, and when they step back out that have "traveled" a significant distances. Basically 1 step in the Hollow equals about 3 metres in the real world. The issue for the Assassins is that stepping into the Hollow in the manner they do, is very "loud" and attracts the inhabitants. Staying too long in the Hollow will result in their death (or worse), as will "teleporting" too often in a short amount of time.
In the Shattering of Aaru, the fragment of Aaru - The First World known as Taphomeh – City of Shadows found itself in the The Hollow. It is the only city in the Hollow and the home of the Eshedim, themselves fragments of the Ehoshim.

Type

Dimensional plane