A device that reveals a discrepancy between appearance and reality is

A device that reveals a discrepancy between appearance and reality is called "irony." Irony is a literary technique where words or situations are used in such a way that their intended meaning is different from their literal or surface meaning. For example, verbal irony occurs when someone says something but means the opposite, often for humorous or sarcastic effect. Situational irony occurs when there is a contrast between what is expected to happen and what actually happens. Dramatic irony occurs when the audience knows something that the characters in a story do not. Irony can be used to reveal a discrepancy between appearance and reality, as it often exposes the difference between what is said or expected and what actually occurs. This can create a sense of tension or humor in the reader or viewer and can be a powerful tool for conveying meaning and depth in literature and other forms of art. Therefore, the answer is: irony.