Netherworld

A Netherworld is a type of world classification mentioned in Every Heart a Doorway. It's unknown what makes a world a Netherworld, though Eleanor implies that they're similar to Underworlds. In the last chapter, Kade says to Nancy that he and Christopher and working on a new map for worlds connected to the dead, with Vitus and Mortis as minor directions.

There are currently no known examples.

Trivia

 * A Netherworld is described as being "the underworld; hell" or "a hidden or illicit area of activity."