The Dwellers are a group of feral-humans found in the pit beneath Butcher Bay. Presumably they are descended from, or actually are, prisoners thrown into the pit! They have no traces of sapient behavior
They seem to be mutated to some extend, either from radioactive waste, or adapting to the extreme environment they live in. They are apparently capable of smelling human blood, and seem to have no problem navigating the dark corridors of their subterranean home!