Which cosmology--the one known and accepted, based on all observable evidence available to the finest natural and esoteric philosophers?
Or the truth?
According to all data available to Waziri mages and other, non-magical observers, there are only and exactly three observable planes: the mortal world, Al-Duniyyah (with the Spirit World as a sort of altered-perspective version thereof); the Elemental Otherworld, Al-Akirah; and the Netherworld, aka "(the) Hell(s)" and "the Abyss". The mortal world and elemental otherworld are globes which orbit stars in different parallel dimensions, which is why their geography is nearly but not perfectly identical. Other stars exist, but are so distant they cannot be reached.
The truth is that this is but one world among many, one plane among many, but
this world, specifically, has been walled off--or, more accurately,
barred up. It is a
prison for something, and (nearly) all transplanar beings
except devils and demons departed it about two thousand years ago, when those supernatural, invisible bars went up. What else lies in the Deep Beyond, no one knows...yet.