I call it...Coffee Break.
It appears around dlevel 25-27.
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It's like a workplace. You start in the foyer, then proceed into a 'holding room' full of former commandos to fry your ass.
The top lever breaks the walls to that little place with all the commandos, and the bottom one is a Meditech lever, a "Coffee Machine".
You then proceed through an office space, with the first lever after the sargant being an open button to the "toilets", where the 4 viles are located. The next lever with the Pain Elementals is another Meditech, the Pain Elementals spawning Lost Souls addicted to the coffee.
You then take out the board of executives (the barons).
On lower difficulties, the Viles are replaced by Hell Knights. On any difficulty but N!, there is no ammo/weapons dropped from any enemy. blah blah can't nuke or phase