For discussion in a different direction, let's say pulling the chain does not zap the puller (like in the other thread/poll).
What do you think would happen when the chain is pulled? What would you consider a legitimate result of pulling the chain in this set up? This is a question mostly for those who would pull the chain without precautions. If not a bad result to the puller, what result? Should it open the secret door?
Bullgrit
Well I like to to hope that the games I play are somewhat logical. If I built a dungeon, I'd see fit
not to include a self-destruct mechanism. And even if - that it'd be at least child-proof.
Similarly, if you make a room with hidden door, then what's the point if they are opened by the single thing anyone can see in said room? Why would you build a room to contain only said chain and doors? Had spare stones?
So we have an empty room with a chain in it. I know that the kind of people who rush in and kill everything that moves but doesn't give quests -
will pull the damn chain. So I say - let the chain drop the ceiling on them. Since the PC-trap is not at the
enterance of my beloved lair, it probably guards something. My phylactery perhaps?
Alternative - it is simply a oversized ringbell. The idea is to make sure that whoever wants to open the door is in the center of room, and thus easily disposed of if he is not welcome (fireballs, concaves in walls with golems inside, that kind of jazz).
(hah, this was going to be an edit, but Bullgrit posted an important qualifier. I see the chain put there by someone, probably designer/builder of this place. DM is simply telling me what I see.)