Adjective
underearth (not comparable)
Beneath the earth; underground.
The Sega Saturn version includes 28 of the 32 single-player levels from the original PC version of the game, though the secret levels, Ziggurat Vertigo (E1M8), The Underearth (E2M7), The Haunted Halls (E3M7), and The Nameless City (E4M8), were removed. Source: Internet
Slated to be an adventure module for use with the Dragons of Underearth system. Source: Internet