In a bit of a departure from conventional D&D, Illirium’s cosmology is a little more materialistic. I’m a fan of the original alignment structure for characters and envision that carrying over into the cosmology of this world. Reality in Illirium can be viewed as a very large onion with many layers. The outer layers represent the eternal, the expansive, and the infinite, which can be considered a manifestation of the good. The farther out the more powerful the inhabitants. The middle layers are the elemental, the material, the place of ebb and flow between creation and destruction. The inner layers are the dark, the hidden, the evil, infernal places of destruction and pain.
The Heavens – The outer layer of the onion, though this outer layer in a sense is so vast as to have no real perceptible boundaries. The heavens are the home of the great unknown, the domain of the beatific. It is a place of chaos and wonder, where the stars speak of a truth but one that can almost never be perceived except by the gifted. The sun, moon and other good gods dwell here though they may venture out at need.
The Ether – The mists and air all about the real and perceivable.
Water – It lies upon the land and permeates it and flows amongst and through it.
The Firmament – The surface of reality where all elements mix.
The Subterranean – The near underworld, where dwarves and gnomes dwell and surface folk visit more infrequently.
Hell – The deep areas, dark, hidden, conspiratorial, strive against the real.
The Abyss – Domain of the chaotic evil, the wantonly destructive and ultimately non-existence.