Deeping Steppes as named by Dargain the Gnomish adventurer who happened upon this place when attempting to find lost friends in a nearby series of caves and was swept in by the unexpected surge of an underground river, perhaps due to shifting of plates or erosion of a natural barrier. The cavern was sealed and unknown until being discovered by Dargain.
This is a region of the underdark where a series of very large plateaus occupy a huge underground cavern. The cavern is situated near a very common and sometimes treacherous underdark route know as The Underway (in my version of the world) which reaches from the Dales to Silverymoon regions in the Forgotten Realms.
People that live in cities no longer have any contact with the gods. There was a pact between the gods, humans, and animals. We could talk to the gods and the trees were the witness' to the pact. When the trees started getting cut down to make cities the pact was broken by the destruction of the witness'. So now only those that live with nature can speak to the gods and/or animals. Some trees grow tall creating darkness that scares men and they are not able to go near them. If they could they could again speak to the gods.