The Festering Nest or Hive, is a cavernous underground area that has been completely infested and befouled by insect-like creatures, that lies beneath the strange-looking growth in the field of Lester the farmer.
The walls and floors themselves are alive, oozing with slime and grossness, and the ground is saturated with toxic, bubbling acid. The barrels that appeared throughout the original game are replaced in the Festering Nest levels with organic body-snatcher-ish pods.
Many of the creatures of these levels blend into the walls and floors, becoming hard to see them until they move. All the creatures are alien in appearance, with mostly insect-like traits and attack modes. An insectoid beast called The Defiler is responsible for the many atrocities in the Nest, and only by slaying it can this place of filth be cleansed.