The PCs will enter a chamber in the dungeon and the doors will lock. A sleeping gas then fills the chamber, knocking the PC's out.. when they awake, they find themselves in a large sound proofed prison cell, bound and gagged in front of the head baddie without their weapons.
The head baddie tells them what is going on.
"Outside there 10 large chests. Each contains one set of your weapons. But don't be fooled by the pictures. They have been randomly placed.
I am going to let you out one at a time. While you are outside, you can look inside any 5 chests before my minions take you to the next cell. The chests will then be closed again for the next person.
You cannot touch the weapons or in anyway communicate what you find to the others. No marking the chests, no shouting, NOTHING! If each of you can find your own weapons, then I will fight you. Otherwise I am booting you back to the entrance of the dungeon with your stuff and you have to do this all over again.
You have three minutes to think about it before we begin."
The baddie then exits the cell and locks the door.
HINTS: "Do you think they will figure out the best way to do this?"
"I don't know. Will they?"
"Well if any of them are familiar with the Prisoner Box Riddle they should recognize this situation and that there is a method with a greater then 35% chance of success for the entire group."
THE BEST METHOD TO SUCCESS: Everyone first open the chest with the picture of your weapons. If your weapons are inside, you're done. Otherwise, look at what's inside and then open the chest with that picture one it. Keep going this way until you found your weapons.
EXPLANATION AS TO WHY THIS WORKS: So if PC Amoz opens the chest to with the picture of the Blood Katana and Krysknife (his weapons) to find the Aurial Bow and Molag Arrows, then he will open that one to find the Volungbal Mace and Arce-Spear, and finally get his weapons in the next one.
Note that if he keeps going, it will take him back to the start. So this is a loop. By starting with the chest with the picture of his weapons, he restricts his search to the loop containing his weapons. And there are decent odds, at least 35% that the entire group as a whole will find what they need in only five guesses or less.