Knights and Knaves

You enter a dimly lit room. At the other end, there is a large door, guarded by two large suits of armor standing still. As you approach, they both slowly animate, and speak in a deep, metallic voice.

“We serve the same god”, says the armor on your left. “We serve different gods”, says the armor on your right.

Both extend their right hand towards you. In their open gauntlet, you see a key.

You remember now the stories. Rumors that the Mage developed an obsession about truth and lies, and built automata, dedicated to Leira, the Lady of Deception, and Savras, the Speaker of Truth.

Which key will you try?

Puzzles, Knights and Knaves

As the players in my campaign were headed into a dungeon recently, I figured it would be interesting to try and throw a puzzle their way. I find puzzles a bit problematic, though. They tend to be trick problems, leaving no way forward if the players get stumped. There is also the issue of the disconnect between the player and character intelligence. What do you do to help a player who is stuck, even though their highly intelligent character should be able to solve the problem in a heartbeat?

I thought a puzzle inspired by Knights and Knaves could be an interesting way around the problem. But first, what are Knights and Knaves? They are a classic type of logic puzzles, in a fictional world where only two types of characters exist, Knights, who can only speak the truth, and Knaves, who can only speak falsehoods. The goal is to determine which character is what, based on what they say. A more complex variation adds a third type of characters, Spies, who do not answer reliably.

So how do you turn this into a dungeon puzzle? In this case, one of the armors is a Knight, and has the right key, which opens the door without problem. The other is a Knave, whose key triggers a trap. None of them will answer questions: When addressed, they will just repeat the same information, over and over again.

I thought this would make a decent puzzle, because no matter what happens, the players can get around it if they get bored with the puzzle itself - at a cost. They can try a random key, or perhaps fight the guardians and break down the door, and risk triggering the trap. This didn’t happen in our game, but I figured we could also use Intelligence checks to drop some hints, for instance “as you ponder about the problem, it occurs to you that if both armors were of the same type, they would both say the same thing”.

What happened?

My fearless adventurers, after hearing what the armors had to say, immediately remembered the classic problem of the two roads, and went into an animated discussion around what to ask the armors. Once it was clear that no question would be answered, they proceeded to pick the wrong key, and trigger the trap as they opened the door.

After that happened, they concluded that the other key was probably the right one, and started to grab it from the other guardian. Thankfully, one of them realized that what this guardian was saying had changed. As it turns out, I decided to randomly reset the keys and guardians every time an attempt was made, and as a result, they had switched roles.

I was initially a bit worried that the puzzle would be too easy. As it turns out, it wasn’t, and worked pretty well. One drawback perhaps is that adventurers could immediately make it through the puzzle, out of sheer luck. In the worst case, they should be able to overcome the obstacle after a couple of attempts. In my view, this is acceptable: they get to choose how they want to approach it, and there is a cost to pay for ignoring the puzzle.

I suspect the same idea could be used in different setups, say, a trapped room or a chest magical lock.


Below is a list of links to various Knight and Knave riddles, in case you want to include them in your own adventures: