What does Failure to Reveal refer to in Magic: The Gathering?

The term "Failure to Reveal" specifically pertains to situations where a player neglects to show a game-required fact. This can happen in various contexts, such as when a certain card commands a reveal as part of its resolution or when game rules dictate that a player must disclose specific information. For example, if a card requires a player to reveal their hand or a certain card from it, and the player fails to do so when required, this infraction falls under "Failure to Reveal." It emphasizes the importance of accountability and adherence to game mechanics that involve transparency among players, ensuring that all game actions are conducted in accordance with the established rules.

The other responses touch on aspects of revealing cards but do not capture the broader definition of game-required information that "Failure to Reveal" encompasses. For instance, simply forgetting to reveal a hidden card or failing to show a card that affects the game focus more narrowly on specific actions rather than the overall requirement to present information as needed during gameplay.