A discrete universal dimension with its own set of rules. This universe may be vast (like the source-hypervolume associated with the Irisians) or it may be small (like the universe associated with Earth) or even tiny (like the Balnibarbi and Malperdys pockets).
Branes may be physically or semantically adjacent, permitting the interference of Darkness between them. This process permits the transfer of Ontons, reality-influencing concepts which steer universes towards parallel or convergent development.
Branes “float” inside the Bulk (another name for the Shift) and are subject to the Aethyric Winds which may move their position in relation to other universes (this can be physically or semantically - limiting the influence of their Ontons.)
Semanticity
While there are potentially billions of each reality, the semantic differences between realities start to amalgamate them. It might be helpful to think of two semantically similar Bulk spaces as physically adjacent or even overlapping. The ontons are able to pass between them easily, subtly influencing each reality.
For example.
Two Earth realities which have very small differences can create a phenomena such as The Mandela Effect, a manifestation of false memories implanted by ontons between the two places or Deja Vu, the feeling of familiarity with new experiences. Some conditions (schizophrenia, autism) may include heightened perceptions of these semantically adjacent realities.
List
Shift Irisian Hypervolume Dreamlands Afterlife Earth-standard, including Barsoom and Apocalypse Earth Earth-40 Faerie The Emerald City Flatland Hyperborea Narnia Carcosa Chthon Zothique Malperdys Balnibarbi Xanadu Oublios Abysson Space