Chance cards are used to create interesting role-play opportunities. During play when a character rolls a critical failure a chance card would be given to the player, chance cards can have positive and negative effects. Typically each card would have a success option and a failure option. Another example is the “Plot Twist” card which generally follows the existing plot but throws in a clue or a bit of disinformation or an odd requirement like “this situation must be solved with an explosion.” Most often the GM will put these together as the adventure is being built so that they will fit with the adventure.