This is two-part "story" campaign. The first map starts with a friendly Hell Knight fighting for his life. After you progress through the level, you may notice that he is not longer in the lobby and a SoulSphere is left on the ground. Make of this what you will. This happens again in the second level. The grand finale in the second level has you fighting alongside a Slaughtaur from Hexen. (He gives you Invulerabiliy when you really need it!)
Video:
The music at the end is "Welcome to the Machine" (dxn-mw-1-machine.it) by David "DavidN" Newton. (DoomWiki, The Mod Archive)
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