Realm of Caverns
Dark caverns, chittering monstrosities, and vast wealth are what lie in wait on Sepulus. This mineral-rich rock has no sky, nor even a sea, just an endless series of natural cave systems and the burrowed structures of insectoid hives. All manner of strange insects call this realm home; each uniquely adapted to endure and process the mineral-rich environment. These bodily processes create the realm's unique geology, including excreted veins of alloyed metals and clustered gemstone nests.
The locations of Sepulus are broken up into "Depths", most of them are named after the dominate species in that region rather than the biome that resides within it. There are a variety of biomes but they are more along the lines of "This has lots of iron" or "This has steel". In Sepulus, there are ores that actually produce refined material such as steel, bronze, or related.
There is no sky. There are no stars. There is only the mound of earth filled with bugs.
Sophontic bugs. Evil shadow creatures that eat fear. There are a group of Manfolk but they aren't anywhere near native.
Fungi, cave moss, glowing orbs of bioluminescent light. Some of the bugs have learned how to farm these plants, but the Manfolk rely on bug meat to survive.
Does it exist as a bug on earth? Then yes. And then add a bunch more.
Primal Earth seems to be what warps the ores into refined minerals. Primal Shadow is found in the terrifying sections of the mound. Glow is weaved by a group of divine spiders that rule the mound..
Each bug has its own tech. Ants are great at construction and military, roaches make massive mounds of stuff and construct haphazard tech, spiders make elegant regions, and so on. The Manfolk are just frantically trying to survive. All Sophontic bugs innately use magic.
Realm of Caverns
The Earth Realms
The Shadow Realms