Once upon a time, there was a greensuit person named Doomguy. Then, after a while, starting from Union Aerospace Corporation, got into a water portal that took him to Mars. There on Mars were a lot of bases with computers and other complex. Once, Doomguy was sent to Phobos because the masters there of UAC have spotted invading zombiemen and imps. Doomguy was then immediately taken to a Phobos base, E1M1: Hangar, to fight against 9 zombiemen, 4 imps and 16 powerfull shotgunners. It continued with base teleportation untill Doomguy reached E1M8: Phobos Anomaly, guarded by 2 Barons of Hell. after that, there was a staircase leading to a portal. Unfortunately, it took Doomguy to The Shores of Hell, rather than ending the game by sending him back to Earth :( Doomguy is now on Deimos, the other moon of Mars, way more UAC bases with invading demons and spectres. It kept getting more demonic, and the demons kept building E2M8: Tower of Babel (on intermission screen), until Doomguy reached the full building, where there was a rocket-launching Cyberdemon. Then Doomguy was taken to Inferno as a punishment from the demons for killing the ruly Cyberdemon. At Inferno, there were rather demonic locations where you had conferences and versus-battles with cacodemons and lost souls. At the end of E3M8: Dis, there was a doorway that took you back to Earth. I'm not sure why you were sent to The Shores of Hell instead of Earth after killing a couple of Barons of Hell. There was hellspawn through the doorway between Hell and Earth, with much more bases to clean out, along that Daisy died immediately due to hell hijacking Earth! (Read more on this page at the Doom II wiki. That's like an elevator (the same thing (page) on multiple floors (wikis)), isn't it!?)