Crabbe (one of Draco's friends) starts fiendfyre (cursed fire) in the Room of Requirement. He is trying to kill Harry, Ron, and Hermione. However, the fire gets out of control and consumes the room,...
Vincent Crabbe destroyed the diadem when he used fiendfyre (cursed fire) on it, while trying to kill Harry Potter (along with Ron Weasley and Hermione Granger).
A lost crown that once belonged to Helena Ravenclaw. Her daughter, the Grey Lady, stole it and took it to Albania where is was considered lost. Lord Voldemort discovered it, turned it into a Horcrux...
Ravenclaw's Diadem is a silver crown with the blue jewels in the middle. See related links for a picture of the film prop that was displayed at Comic Con 2010.
Its like a crown or a tiara inscribed with the words "Wit, beyond measure, is man's greatest treasure." Rowena Ravenclaw used to own this when she was alive. It it one of the horcruxes. It is...