Riddles challenge the participants to find out, how the work or what is behind their story. They have to solve the mystery cooperatively togehter or each player by himself. While such games can occupy players often for a longer time, they can typically be only played one time until the mystery is solved.
Some prominent riddles are listed here. You can find a complete list of all riddles in the GamesWiki in the category:riddle.
A group of explorers fly across the arctic ocean over the ice. They can see several ice holes, polar bears and fish. But how many can they see?
Johnny loves certain things, but hates others. What does he love and what not, and why?
Black magic enables the participants to read each other's minds. How can they do that?
An object is handed over either open or closed. But when is it open, when closed?