The Underdark
“Light and dark is balance...but what if there's too much of one?”
The Lightless Lands.
History
The Underdark is an enormous system of subterranean caves, caverns, and tunnels located beneath Val'darin. Similar to many naturaal formations on the Material Plane, in the Shadowfell, there exists a Shadowdark.
The Underdark is split into three sections: Upperdark, Middledark, and Lowerdark. The Upperdark is 3 miles below the surface and where Odron was first founded. Access is through subway tunnels or elevators, Bulks provide protection for any monsters that attempt to get in cities along with fortifications such as walls and advanced technological systems.
The Middledark is located 4 to 10 miles below the surface, this layer contains much of Odron's industry buildings.
The Lowerdark has been placed on restriction, only licensed adventurers with proper paperwork can access these dangerous areas. While a lot of monsters have been recorded in the Lowerdark, many of them haven't been written down. Access to the lowerdark is blocked by metal gateways, Bulks, turrets, guards, cameras, and motion detectors. If you think it's impossible, it happens in the Lowerdark.