The Netherhells are the Mephitist underworld, populated by demons and the damned souls of Unseelie elves. There are actually nine Netherhells, arranged in descending layers, with the first and mildest being on top, and the ninth (and most horrible) at the bottom.

The Netherhells are believed by some to be a purely metaphysical concept, but others insist that they literally exist and can be visited under certain circumstances by the living.