Boundaries

From Sword of Truth Wiki

The Boundaries were the result of a spell that raised the underworld to the world of the living. In effect, it created a boundary that no one could cross without getting lost to the underworld.

A creature called Hearthounds were creatures that lived in the boundaries and could escape at night. Until the boundaries started to fail, the hearthounds couldn't venture very far from the boundaries. To make sure the hearthounds didn't kill an innocent by standard, Boundary Wardens were created to kill hearthounds that did get to far out.