As the last man standing, the player character fights through the onslaught of demonic enemies to keep them from attacking Earth. In "Knee-Deep in the Dead", he fights through the high-tech military bases, power plants, computer centers and geological anomalies on Phobos. It ends with the player character entering the teleporter leading to Deimos, only to be overwhelmed by monsters. In "The Shores of Hell" he fights through installations on Deimos, similar to those on Phobos, but warped and distorted from the demon invasion and interwoven with beastly architecture. After defeating the titanic Cyberdemon, the marine discovers the vanished moon is floating above Hell. "Inferno" begins after the marine climbs off Deimos to the surface. The marine fights his way through Hell and defeats the Spider Mastermind that planned the invasion. A hidden doorway back to Earth opens for the hero, who has "proven too tough for Hell to contain". However, a burning city and a rabbit's head impaled on a stake (named in "The Ultimate Doom" as the marine's pet rabbit, Daisy) show that the demons have invaded Earth. In "Thy Flesh Consumed", the marine fights the demons on Earth through a variety of disconnected high-tech bases and demonic temples, though ultimately the forces of Hell prevail in the invasion of Earth, setting the stage for "Doom II: Hell on Earth".