Puzzles that focus on getting information from truth-tellers (who never lie), liars (who always lie), and/or Jokers (who answer at random), or which use such characters as an integral part of the puzzle.
The most common form of a puzzle with this tag focuses on getting information by asking questions to members of 2 or 3 of the following groups:
- Truth-tellers (or Knights), who always tell the truth.
- Liars (or Knaves), who always lie.
- Jokers, who answer at random.
The questioner doesn't know who they're asking — Knight, Knave or Joker — and often only yes/no-questions (or similarly restricted questions) are allowed. Restrictions on the number of questions asked are also common for these questions.
This tag can also be used for puzzles which have liars, truth-tellers, and/or jokers as an integral part. Some examples of this type:
- Murdered down the Rabbit Hole (a long logic puzzle) is a mystery logic puzzle where not all of the clues are truthful. Part of the puzzle is determining which clues are lying.
- You trolls, get out of my party! is a strategy puzzle where trolls (who answer at random) must be identified and expelled from a party that also contains friends (truth-tellers)