Lunacid

A terrible beast rose from the sea and breathed a poison fog across the earth. In the centuries since, those deemed undesirable by the society above have been cast into a massive underground well — a lightless pit that has become a breeding ground for disease, monsters, and stranger things. You awaken at the bottom of this well, the circumstances of your exile unclear even to you. The only way out is down: past the creatures that have made their home in the dark, through the ancient subterranean world below, and finally to the sleeping old one at the very bottom, who has been waiting there for a very long time.