Sybill Trelawney introduced all third year students to this device and its proper use in 1994. However, most students, Harry Potter and his friends in general, saw nothing more than the white blank swirl in it, and Ron joked about how that night would be very foggy. In their end of year exam, the third years had to look into a crystal ball and predict the future. Harry lied and said that he saw Buckbeak getting off his trial that night. Professor Trelawney then made a prediction, one of the two proper ones she had ever made.