DND: Sublands

You wake up laying down in grass. The world around you is strange. Vast and intricate paths and cave systems. No one goes above ground due to the poisonous atmosphere, as well as the creatures that occupy it. That isn’t all, though. There are strange civilizations, underground biomes that stretch, flora that consumes, fauna that speaks, and mysteries that don’t wish to be solved. Do what you will, the power is yours. (Honestly, this is my first story. Have fun, describe your character, do whatever, and if you have any suggestions, please comment.)