Selecting 'Hell on Earth' propels the player into the classic 32 map Doom II campaign, whereas selecting 'No Rest for the Living' starts the new 9 map addition.
The new maps are a separate selectable campaign at the inception of the game, in a fashion similar to Doom's episode selection. As Doom II did not have episodes per se, calling No Rest for the Living an episode is technically a misnomer. The episode consists of nine levels in all, eight standard levels and a single secret level, as a homage to the similarly structured nine-map episodes in the original Doom, particularly Knee-Deep in the Dead.
