Helena Ravenclaw, known as the Ravenclaw house ghost, or the Grey Lady, was the only daughter of the famous Rowena Ravenclaw, fonder of Hogwarts. Helena was obsessed with being perceived as better then her mother. She had hoped to one day, be considered even more brilliant then her mother, unfortunately that day never came. Over time Helena grew restless, and decided she need to act. It was reported the she stole her mother's diadem, an object enchanted to permit the wearer excessive wisdom and knowledge. She then fled to Albania.

Rowena, to proud to admit the truth, convinced others she still had the diadem, and never revealed her secret. Overcome with grief at her daughter's betrayal, Rowena soon fell ill, and requested that she see her daughter one last time before her death. Rowena then sent (the present Slytherin Ghost) the Bloody Baron to retrieve her. The Baron harbored unrequited love for Helena and became enraged when Helena refused to return with him. Out of his anger he murder Helena, and then after realizing what he had done, he killed himself.

After her death, Helena returned to Hogwarts. A particularly temperamental ghost, Helena was extremely untrusting of everyone except for a select few. It is known that Helena does not speak to students unless they're in house Ravenclaw. Two wizards known to have 'befriended' Helena were Luna Lovegood, and Tom Riddle. All though in the end Helena learned that Tom had deceived her, it was too late. Tom Riddle had become interested in the Diadem. He charmed Helena and gained her trust, until eventually she revealed the location of her mother's Diadem. Upon retrieving the artifact, Tom Turned into a Horcrux, thus bringing even more shame and guilt upon Helena.