As a fantasy-kitchen-sink setting, Aerb of course has a variety of parallel realities and elemental planes. Only a couple of these are super-relevant to the main events of the plot, but I made a little inset diagram of the elemental planes to fill out a corner of the map, and this simple little planar map is worthy of a bit of discussion for its own sake.
Ron Shelbi's cosmological model of Aerb:
AerbPlanarCosmology.png
This little map was made entirely in Inkscape.
The list of planes is canonical, but the arrangement is a bit of my own invention. I imagine it to be the kind of model that's outdated for serious academic wizarding work, but is still culturally emblematic of the the elemental planes, and is used is art and education.
One of the running gags is that echoes of our world show up on Aerb, but with subtly different meanings or connotations. For example Aerb's trade language is "Anglish", which is almost but not quite the same as modern-day American English. I wanted to stick with that theme, so I used real-world astronomical symbols as symbols for the elemental planes. In particular, I used glyphs from the Catrinity typeface. Some of these symbols are the familiar symbols for the planets, but most of them are the lesser known asteroid symbols. (Scientists stopped assigning symbols to asteroids when they realized there were thousands of the things.)
The exception is the symbol for the Elemental Plane of Chitin. The symbol for the asteroid 16 Psyche is conceptually appropriate, depicting a butterfly's wing. But to be honest, it's not a very good depiction of a butterfly's wing, so I made my own icon inspired by the mission patch for NASA's upcoming Psyche Mission. By slightly displacing the geometry, I think I managed to make a simple little glyph that's simultaneously evocative of a butterfly's wings and an ant's antennae.