Similar to the story of Doom 2, the demons from Hell invade Earth. According to Id Software, they hoped to expand the Doom story much more than in the earlier Doom games. Places where the player goes include Earth, Mars, Phobos (one of Mars's moons), Sentinel Prime, Argent d'Nur, Nekravol, and even the game's version of Heaven, Urdak. Some of these planets have been taken over or are being taken over by the Hell dimension.