Takes place after the events of Doom 64, assuming Doom 3's story takes place instead of original Doom's, as well as RoE, Doom 2, Final Doom, and Doom 64. Please note that many objects in the map can be examined. I'll make it easy for you and tell you to check out the red terminals, any notepads you come across, and some other computers in the personal quarters...the ones you can flash so that they stand out a bit. It's an attempt at fleshing out the story, but is also optional. Also, I plan to make many more maps to continue this series.
As you watch the demonic craft lift off in the distance, you decide that staying in Hell wasn't such a good idea after all. It vanishes from sight, leaving you to find another way to tail them. After backtracking, you find a teleport leading back to a Mars base, where you acquire a working ship and match course and heading with the demon ship. The ship lands near a small base in a canyon on Earth, where you hop out and try to find out what the horde is planning.