When you're putting together a puzzle for your RPG, there are tons of ways to handle it. A really easy and supremely adaptable puzzle to use is Mastermind. Wikipedia tells me it's also called Bulls and Cows and goes back a over century. It's similar to Twenty Questions, Hangman, or Guess Who?, which make good puzzles for RPGs as well.
You can adapt Mastermind to a lot of different situations. It can be numbers or letters in a password; words in a passphrase; potions on a rack; symbols on tumblers; or colored marbles in bowls. Fallout uses a variation of it for hacking terminals.
As a reminder, never make it possible to fail to continue the game. If the puzzle guards the door into the dungeon, then failing to solve the puzzle has to cause some problem other than preventing the PCs from getting in. If you're familiar with my article on skill challenges, you can use some of the same hazards from those in guessing games.
Here are the basic rules of Mastermind:
- There is a secret code. It's usually fairly short.
- The code is made from elements drawn from a set. The set can be fairly large.
- The player(s) get to make a pre-determined number of guesses. They don't have to know how many guesses they get, or how many are left. In D&D, you can also cause them some other penalty on a failed guess.
- The way the players make guesses can have additional rules. A passphrase should be a grammatically correct phrase (Praise to Tiamat instead of Tiamat Praise Praise), repetition may or may not be allowed (If you have one icon of each color of chromatic dragon, you can play black, white, red; but you can't play red, red, white), and length may or may not vary (if there are three bowls to put liquids into, the length is always 3; but guessing a password might involve words of varying length).
- After each guess, they get feedback about how close their guess was to the secret code. There are a few ways to give feedback. If length is a factor, there must be length feedback.
- Length: Too Long, Too Short, or Correct Length (always use when length is a factor)
- Correct: The number of correct elements in correct positions
- Wrong Position: The number of correct elements in incorrect positions (optional)
- Omen: If the code has meaning, a fourth feedback option is to give a hint as to how close to the meaning the guess is. For instance, if the passcode is a word of six letters, "DEFILE" the puzzle feedback could deem hopeful or positive words weak and cowardly.
- Difficulty varies based on the above factors:
- Giving more feedback makes the puzzle easier,
- Giving more guesses makes the game easier,
- Using a smaller set makes the game easier,
- Using fixed length makes the game easier, and
- Using a shorter code makes the game easier.
A Mastermind Example
In the cult's library is a scroll on metaphysics. Some of the words on the scroll have been circled in charcoal pencil: "Curse, Praise, Glory, All, For, To, Tiamat, Harpers, Tharzidun." There are three puzzle rooms, each with a statue of a robed cultist standing in front of a door. You can't get through the door unless the statue animates and moves out of the way. An Insight check tells you that the nine words make up the passphrases to each puzzle door, but which words for which doors?
The code phrases are...
North: ALL PRAISE TIAMAT
East: DEATH TO HARPERS
West: THARZIDUN FOR GLORY
This is a fairly easy puzzle: There are only 9 words in the set and 3 puzzles. The puzzle will get easier as the players go on, because they will rightly assume the proper nouns (TIAMAT, HARPERS, THARZIDUN) are only used once. Also they will assume the passphrases make sense (not FOR FOR TO ALL FOR or other nonsense phrases). They might also easily guess the phrases are 3 words each, since it's hard to construct longer phrases with the words in the set. So to raise the difficulty, we will give the players a small number of guesses.
"The cultist statue has two ruby gems for eyes"
Stealing the gems does no harm to the thief, except it means the PCs can't get any hints. They have to speak the password. Each time they get it wrong, some part of the statue becomes colored and lifelike. This represents an incorrect guess. If they get it wrong four times in a row within 24 hours, the statue comes fully to life and attacks them. If they attack the statue or try to shove it aside, it comes to life and attacks them. In addition, other traps in the room might activate. Statues tend to be immune to poison gas...
The reason we're using "statue attacks" instead of "statue stops taking guesses" is that we don't want failure on the test to mean the adventure ends. Also, we want to make the puzzle hard. We want the PCs to fail at least one puzzle. So we have to have the failure condition hurt the PCs a little without stopping the game.
We're only giving feedback on two things: Length and number correct. First, the statue gives feedback (if there is feedback to give) after someone faces it and speaks three words. Second, the statue gives feedback about the number of correct words in the correct positions. Its eyes will light up when you start to talk to it. After three words, both eyes fade to dark if no words were correct. One eye will stay lit and sparkle for ten seconds if one word was correct. Both eyes will stay lit and sparkle for ten seconds if two words were correct. Getting three correct makes the statue animate and open the door for the PCs.
More Puzzles for your Games
Here is a long list of other games people play that you can use as RPG puzzles.
Hidden rule games involve playing a game where there are hidden rules. They require an active judge. In RPGs, these work well for simulating hacking or a sphynx guardian's puzzle. Some can go on until the rule is solved, and others end eventually. You can play some competitively, so that one player is the winner. And others force all the players to cooperate against a time or guess limit. Some can work either way.
- Zendo is a really simple rule-guessing game that has pretty plastic pyramids. It really focuses on the act of testing and guessing a rule. Zendo is competitive, but you can make it collaborative by assigning some cost to guesses or limit to the number of guesses.
- Elephant's foot umbrella stand is another rule guessing game you can use. Like Mao, there are one or more people who know the hidden rule. You can use a whole village of people who keep a secret. They carry or speak the name of an object to be let into an inner sanctum. Lots of different objects let them in, but no two objects can be the same (so the PCs can't just copy someone).
- Eleusis is a rule-guessing card game you can use as a riddle contest against a sphinx type riddle giver.
- Mao is a card game where new players have to scramble to figure out the rules. If the PCs visit a tavern in an unfamiliar city, you can emphasize the exotic nature of the city with this game.
- Green Glass Door: This is a simple kids' word game where you have to figure out what nouns can pass through the "green glass door." Spoiler alert: It's nouns with double letters (e.g. letters can, but words can't). You can invent similar tricks. A portal that only allows certain things to pass is very appropriate for Planescape.
Guessing games involve a secret keeper and a guesser. Some are played competitively (battleship, guess who) while others are asymmetrical (hangman, twenty questions). Competitive versions end when one player wins. Asymmetrical versions end after a limited number of guesses has been used or the correct answer has been guessed. You can turn a competitive game into an asymmetrical one or vice versa. Ulam's game is unique in that it is a game of twenty questions where the questions and answers are already asked, but one answer is wrong. The player(s) have to guess the solution, like a game of twenty questions, but to do so, they have to figure out which question was answered incorrectly.
- Guess who is a great way to simulate information gathering. Each day, the PCs get to make Charisma checks (D&D) or Contacts rolls (Fate) etc. to ask a question. As they collect answers, the picture of their suspect becomes clearer. But each day, they have to roll for a random encounter or some other cost accrues. Maybe they only have four days to solve the crime...
- Hangman is the simplest word guessing game, with a grim, medieval theme.
- Twenty questions is a great game to play with a sphinx.
- Ulam's game is like twenty questions, but doesn't require an interlocutor. The questions have been asked and answered, but one answer is wrong. The players have to figure out by deduction which answer is wrong, then figure out what the solution is.
- Battleship is a logical process guessing game. You can use it to simulate searching a ruin or wilderness.
- I Spy is the simplest guessing game. It could work for a riddling NPC.
Limited communication games are great puzzles to throw into an RPG.
- Charades is a method people can communicate without a shared language. This is a great way to put a puzzle into your game: Introduce a potentially friendly NPC that you have to use Charades to communicate with!
- Taboo requires you to communicate a password or phrase without using the actual words of the solution. Magic can prevent a character from saying a specific word. But if you're careful, you can help others guess it.
- Heads Up is like reverse Taboo, and you can use an index card to play it.
Asymmetrical information games are games that divide your players up. Generally you give one team (or one player) a problem that can only be solved by the other team's help, except that there is information that's kept secret.
- Building instructions: Divide the teams up. One team gets something built from blocks or drawn on grid paper. The other team has to make an exact copy using a set of blocks or a grid paper and pencil. The first team can't show the second team the original - they can only describe it.
- Keep Talking and Nobody Explodes is a video game based on this premise. If it's not being used in LARPs as a bomb defusing simulator, it will be soon.
- You can use visual memory in a similar fashion. For instance, give a player a map of a maze with all the traps, secret doors, and dead ends marked. Tell them they're not allowed to copy it or write any notes down, but they have to memorize it. Take it away. Then put the PCs into that maze, with all the traps, secret doors, and dead ends exactly where the map said they were. Give them a limited time to get through the maze so they can't proceed with caution. See if the one player can remember enough to keep the party safe.
- Similarly, you can play telephone with the map. Hand the GM map of the maze (with all the secrets revealed) to a player. Give the player just two minutes to copy it as best they can. Take away the GM map. Hand player 1's map to player 2. Give player 2 just two minutes to copy the map player 1 made. Take away player 1's map. Hand player 2's map to player 3. Give player 3 two minutes to copy player 2's map. Repeat until you have a hasty copy of a hasty copy of a hasty copy (etc.).
- Ultimatum game: There's a pool of money. One player makes a single offer. The other player can accept or refuse. If they refuse, neither gets any money. You would pit the players against one another in this game. Otherwise it's no fun.
- Haggle: This is an asymmetrical negotiation game you can use to simulate an asymmetrical negotiation.
- DitLoID: These are neat because a person who lives in or uses the space needs some hint to remember the passphrase, say, "five fingers on the hand" so they abbreviate it to 5FotH. See the link for a ton of examples.
- Word Ladder: Could be symbolic. How fast can you connect Bahamut to Tiamat?
- Word Search: I once built a word search so that the words were the names of all the good gods. The letters left over spelled out the passphrase that was the solution to the puzzle.
- Ciphers: Letter replacement and Cesar shift ciphers can be solved. The longer the plaintext, the easier the code is to crack. Very short plaintext may be impossible to crack. You can give the players a partial key, or let them have one letter of plaintext with a successful Intelligence check.
- A Rebus represents words as images you have to interpet to form a passphrase or plaintext solution, so it can simulate deciphering heiroglyphs.
- Balance puzzles, water pouring puzzles, and river crossing puzzles are logic puzzles. They require the players to think through an analytical problem.
- Latin squares are arrangement puzzles - like Sudoku, but with colors, letters, or even images.
- Nonograms are like Latin squares in many ways, except that the solution is an image made of colored blocks. They could be used to simulate divination or other procedures that result in an image coming from nothing. The players can stop solving once they've got enough of the picture to know the answer to their question.
- Tower of Hanoi (simple sequence puzzle) is a famous puzzle that tasks the players with moving a stack of discs from one post to another.
- Complex sequence puzzles (Rubik's cube, etc.) are too complicated for RPGs, unless you're running a certain weekend-long game at MIT.
- Physical puzzles (tangrams, packing puzzles, jigsaw puzzles, blacksmith's puzzles aka disentanglement puzzles) can be bought at most toy and game stores. They were common in medieval times, so the metal ones you can get at renaissance faires can be diagetic puzzles handed to a player's character.
- Chess puzzles are fun if the players like chess, and chess is a game in your world.
- Solitaire can be a challenge for your game. About 4 in 5 games of Klondike solitaire are theoretically winnable, but the probability of winning is just around 2 in 5; can be played with Tarot cards with the trumps as their own suit.
- Card games can be used as puzzles, or played at the table to represent the PCs' gambling. An important NPC might play a game of Baccarat or poker against the PCs in a spy game, for instance. You might see it as a roleplaying opportunity paired with a battle of wits. Use the card game to frame the scene. Non-betting card games like bridge are often used as frames for the parlor segment of murder mysteries in fiction. Bridge puzzles are potentially interesting puzzles, but like chess puzzles, may be too hard if the players aren't bridge players. Magic: the Gathering card puzzles exist, and have a fantasy theme, but again, your players need to be familiar with the game.
- Mao and Eleusis, above, are hidden rule card puzzles.
- Playing cards can be used as props in number puzzles, if your players like those.
- Crossword puzzles are riddle games. Instead of using a whole crossword puzzle, read through the clues on a few to find riddles of varying challenge level. They get easier if you reveal a few letters in the solution, of course.
- Math riddles: See balance, water, and river crossing puzzles, above.
- Riddle trading: Riddles have real value in a medieval world, and their value scales with the wealth and power of the person "trading" for one. Riddle games where one party tries to stump the other are a classic way of trading riddles for riddles, but NPCs (especially dragons and the like) might give prizes or boons to characters who can stump them with a riddle. This makes the players try to stump you, which they will enjoy.
- Logogriph riddles are very complicated and awfully challenging riddles. They're similar to cockney rhyming slang (see also: Planescape) where meaning is concealed behind a few steps of word play.
- Situation puzzles (minute mysteries) are some of the most complex riddles. They often have multiple solutions, but only one simple solution. The players in a situation puzzle usually get to ask questions, so eventually they will get closer and closer to the answer. A minute mystery might just have a handful of hints you can choose to read or not.
- A Droodle is a visual riddle similar to a situation puzzle. You can find them on google. I just wanted an excuse to write "google: droodle"
- Want the best riddles? Reddit is the best place to find riddles because their system of upvoting moves the best to the top