The cosmology of Epic D&D and Ludos involves the belief and presence of different planes of existence.

The main dimension that we exist within is called the Mortal Plane (or Prime Material Plane). This is mirrored by two altered planes known as Arborea (the Beastlands / Feywild) and Umbra (the Nether / Underdark). Different folks refer to the same locations with the names from their respective cultures.

Most of the Elder Eight deities of The Pantheon have their own respective domain where the souls of their worshippers and the worthy can spend their afterlife.

When souls pass on but have yet to reach an afterlife realm of an Elder Deity, they may be found wandering in the Lakebed. This plane is unfathomably deep beneath the world strewn with fog and wandering, lost, shade-like souls. Contrary to its name, it is said to be dry, cavernous, and seemingly limitless in size.

A mirror of the Lakebed is the Caldera. This plane has been overtaken by the hierarchies of warring and conquering fiends, so it is built up with whole devilish kingdoms. In the center of the crater, it is wildly hot with rivers of boiling blood, but rapidly cools down to icy and permanently dark areas nearer to the edges.

Within the spaces between these dimensions exists the Ethereal (Astral) plane. Some creatures and magics are able to travel on this transitory plane and one can witness nearby entities, but not interact with them.

Beyond all of these is the Primordial Sea (Far Realms) that is formless and sits the cycle of destruction and creation.