In my realm the underground or subterranean areas of the mortal world, Aeris, are more like Earth than the Underdark of D & D or even the areas underground of Tolkien’s world. Here are some things you will find in the subterranean areas of Aeris:
Some Ameyan bunkers. These sites can house anywhere from a few hundred to several thousand people. They are very hard to get into, extremely defensive.
Some temples to gods – usually gods of Malice or ancient, dead gods
Some hiding places where people were waiting out a calamity, or trying to survive from some attack – some are carved into stone/bedrock, some are stand-alone citadels, some are a mix of built up and carved in
A few to several cities of various kinds
Some creepy-crawlies
Some dragons
Some places that act as rifts between the Demi and Mortal Planes and temporary camps/trading posts there.
Mostly underground are Dwarven mines and kingdoms
Some goblins
Some goblin and ameyan settlements, some goblin + ameyan +dwarven settlements
Some ancient ruins here and there
Liches and their crypts/tombs.
Rivers and bodies of water.
In general the subterranean areas of Aeris are not another world to explore. Again, more Earth-like, less LOTR and D&D.
