I am hardly an expert on Rainbow in the Dark, this being my second completion, but we stumbled onto something none of us heard of before -- and it would be pretty hard to miss. So I think the quest was modified in the latest update.
The entire corridor is blocked by a curtain of blue light. The curtain is translucent, so we can see it is actually a vertical cylinder as wide as the corridor -- no way to bypass it. One of us (a cleric I think) steps in and disappears. On voice chat we hear "I am in lava!" He dies.
Without quite thinking things through I cast Resist Fire (Ranger 15, so my resists are pretty high) and step into the curtain. Teleport, and I find myself dropping onto a small platform in a lake of lava. 5 or 6 fire elementals are throwing fireballs at me. I say to myself "Don't panic!" and start drinking pots/cookies. Ten seconds later my red bar is still in good shape, so I grab my Icy Burst bow of GEB, and start slaughtering fire elementals one by one. As I do so, the rest of the party drop in, and all but one die. The room has no exit so I wonder how I will get out. I kill the last elemental, two of us pick up the stones, then more elementals spawn (only two, IIRC). When I killed those, everyone dead and alive teleported back into corridor. I don't remember how we managed to bring them back to life -- I think the other survivor used res clickie on the cleric.
Later in the quest we came onto another blue curtain. This time we knew what to expect, and killed all fire elementals without deaths. As I said, none of my companions ever saw anything like that before.