The following events occurred in the 11th century: * Salazar Slytherin creates the Chamber of Secrets and abandons Hogwarts. * Helena Ravenclaw steals her mother's diadem and flees Britain. After hiding the diadem inside of a tree in Albania, she is killed by The Bloody Baron, who then commits suicide. Rowena Ravenclaw passes away not long afterwards. * A Gaelic poem on Creaothceann is written. * Gertie Keddle watches and writes about one of the first primitive games of Quidditch.