cool story, bro
i never heard about that death room but it's a fun fact
i've played Deus Ex first time just in 2019 and before i only heard about this franchise even i was old enough to beat this game in the release year

I skipped the first Deus Ex for years (blasphemy, I know) but there was so much hype about it I figured I better dip in on the second one. I actually didn't play it until well after it was released, either. At that time I had not played an Origin-like type of immersive sim game in so long that I was still in "Counter Strike mode," and was sure that if I just kept killing everything in site eventually I would come out on top. It's easy enough to kill some of the big players in Act 3 like Nasif and Li Chen, but I spent a long time glitching and sitching to get the Chairman, and then for TWO YEARS I thought the game only had three acts. When I replayed it I was like "da fuq dis Antarctica base?" and now the final acts still feel new to me.

The dance club I think is the "death room" where everybody that gets killed throughout the game gets teleported to. The hidden ending is super weird. I think it has a Helios that hasn't merged with JC, and the description of the Collapse is different when you talk to it.

i didn't find any info about it. anyway, it sounds like typical "fail ending" in games. btw, there is another one secret ending or it's more easter egg. i don't remember how to get it but in the end of the game every character just dancing in a club.

There is a hidden fifth ending. If you can manage to kill all the leaders in Trier, you can end the game in the third act for an extra bad ending. No one knows about it and I've only gotten it twice.