Rowena Ravenclaw, one of the 4 founders of hogwarts and she was known for her brilliant mind and love of learning. Ravenclaw encourgaes these qualities in its students, and as a result ravenclaw now has some of the cleverest and highest achieving witches and wizards at hogwarts. Her diadem of ravenclaw is the symbol of ravenclaw but it is also known as the lost diadem of ravencalw as not a person alive had seen it after tom riddle also known as voldemort retrived it for heelan ravenclaw (rowena ravenclaws daughter) after she stole it from her mother and took it. The bloody barron who was sent by Rowena Ravenclaw to find and return her runaway daughter, Helena ravenclaw tragedy struck when she refused to go home with him, ending in her death after the bloody barron killed her. The Bloody Baron then killed himself in deep regret. he then returned to hogwarts as a ghost with  chains to symbol grief and still to this day haunts hogwarts.