This is area within Greyhawk where the campaign is taking place. It is a frontier region, with no formal rule after the ancient kingdom of Neroth crumbled. This area was almost forgotten as Neroth kept it under tight lock and key for some unknown reason.
However, now all gates have long been destroyed, and the countless caves, dungeons, and Nerothian keeps are all inhabited by one creature or another. The only thing that matches the endless amounts of treasure to be found here, is the endless amounts of danger that is also present.