chthonic

Chthonic might seem a lofty and learned word, but it's actually pretty down-to-earth in its origin and meaning. It comes from chthōn, which means "earth" in Greek, and it is associated with things that dwell in or under the earth. It is most commonly used in discussions of mythology, particularly underworld mythology. Hades and Persephone, who reign over the underworld in Greek mythology, might be called "chthonic deities," for example. Chthonic has broader applications, too. It can be used to describe something that resembles a mythological underworld (e.g., "chthonic darkness"), and it is sometimes used to describe earthly or natural things (as opposed to those that are elevated or celestial).