Fun puzzle. It seems like the disarming mechanism could be a little better thought out. "Touch this ring with the magnetic bar to lower the acid wall" just seems to be an odd way to disarm the acid wall. Either way, I love unconventional traps that make players think.
New solution!
The player reaches through the acid wall, removes the stone, and gently lifts one end of one of the bars closer to the acid wall. The player can then place any metal object on her side of the acid wall to see if the bar and object pull towards each other. Since the acid wall doesn't negate the magnetism, they can test it without passing any object through the acid.
Interesting but a bit too basic to make the typhical player group get enthused about solving the problem.
The main Issue I find with "real" puzzles is sometimes the characters are supposed to be brilliant mages or scientists, (or super heroes) and the player becomes frustrated when their character could easily solve a problem they are struggling with, it really kills the immersion for them.
NPCs (Minor) (Domestic/ Craft)