MAP31: Cyberden is the first secret map of The Plutonia Experiment. It can be reached via MAP15, and uses the music track "Sign Of Evil" from Doom. The map is named for the four Cyberdemons it contains. They start in visible but inaccessible cages where they can't be hurt or attack the player; through out the map they will be released. The pre-level text for this level states: You've found the second-hardest level we got. Hope you have a saved game a level or two previous. If not, be prepared to die aplenty. For master Marines only.