|Pointed purple crystal|
Supposedly a protective device, probably useless
A pointed purple crystal was among the protective devices being sold among the students of Hogwarts School of Witchcraft and Wizardry during the 1992–1993 school year, supposedly to protect against the monster that had been unleashed from the Chamber of Secrets. Neville Longbottom purchased this crystal from one of the other students. When it was pointed out to him that he was pure-blood and thus unlikely to be attacked, he retorted that the monster's first victim was Mrs. Norris, and that his lack of magical prowess made him akin to a Squib.