When can a card be transformed in a game of Magic: The Gathering?

A card can be transformed in a game of Magic: The Gathering specifically when it is a double-faced card and a spell or ability instructs it to transform. Double-faced cards have a distinct characteristic: they can exist in two different card forms, which players can access based on certain game conditions.

In standard gameplay, the transformation occurs when a specific condition is met, usually through a spell or ability that explicitly states to transform the card. This mechanism ensures that the transformation is not arbitrary, maintaining the game's balance and strategy elements. For example, a spell may require a certain condition related to how a creature is tapped or the type of card in play before permitting the transformation.

This allows players to incorporate strategic decisions and timing into their gameplay, leveraging the unique abilities of double-faced cards and enhancing the overall experience by encouraging interaction based on game rules.