Ravenclaw's Diadem

• Type: Horcrux, Founder's Object
• Owners: Rowena Ravenclaw, Helena Ravenclaw, Tom Riddle (Lord Voldemort)
• Maker: Rowena Ravenclaw

Ravenclaw's Diadem was a beautiful, delicate silver tiara inlaid with a large, oval-shaped blue sapphire. It was described as being graceful and elegant in its original state. Engraved upon its surface was the famous Ravenclaw motto: “Wit beyond measure is man's greatest treasure.” When Harry Potter discovered it in the Room of Requirement, centuries of neglect had left it tarnished and aged, appearing as a “discoloured tiara.” Despite its condition, its beauty was still discernible.

The diadem was imbued with powerful magic by its creator, Rowena Ravenclaw. Its properties changed drastically after it was turned into a Horcrux.

• Original Properties: The diadem was enchanted to increase the wisdom of the wearer. This magical property was legendary and was the primary reason Helena Ravenclaw stole it from her mother, hoping to become wise and important herself.
• Horcrux Properties: After being retrieved by Tom Riddle, the diadem was cursed and transformed into one of his seven Horcruxes. He sealed this transformation by murdering an Albanian peasant. As a Horcrux, it contained a fragment of Lord Voldemort's soul, making it an object of profound Dark Magic. This granted it a form of malevolent semi-sentience and rendered it incredibly durable, resistant to most forms of magical damage. Only exceptionally powerful destructive forces could destroy it.

The diadem was created by Rowena Ravenclaw, one of the four founders of Hogwarts School of Witchcraft and Wizardry. Her daughter, Helena Ravenclaw, grew jealous of her mother's intellect and renown. Believing the diadem was the source of this wisdom, Helena stole it and fled to Albania. On her deathbed, a grief-stricken Rowena Ravenclaw sent a man who had long loved Helena to find her: the Baron. The Baron tracked Helena to a forest in Albania and begged her to return. When she refused, he flew into a rage and murdered her. Overcome with remorse, the Baron then took his own life. The two later returned to Hogwarts as the ghosts of Ravenclaw and Slytherin houses: the Grey Lady and the Bloody Baron. Before her death, Helena had hidden the diadem inside a hollow tree. For centuries, its location remained a secret, known only to her ghost. In the 1940s, a young and charismatic Tom Riddle charmed the story out of the Grey Lady. He travelled to the Albanian forest, found the diadem, and turned it into a Horcrux. Years later, when he returned to Hogwarts to request the Defence Against the Dark Arts post from Albus Dumbledore, he took the opportunity to hide the diadem in the Room of Requirement, believing he was the only one to have discovered the room's “room of hidden things” configuration.

The diadem first appears, though unidentified, in Harry Potter and the Half-Blood Prince. While hiding his copy of Advanced Potion-Making, Harry Potter places the “discoloured tiara” atop a stone bust to mark the location of his book within the cluttered Room of Requirement. In Harry Potter and the Deathly Hallows, Harry deduces that Voldemort created a Horcrux using a founder's object from Ravenclaw. After speaking with the Grey Lady, he learns the diadem's history and its fate. He then makes the connection to the tiara he saw a year earlier. During the Battle of Hogwarts, Harry, Ron Weasley, and Hermione Granger enter the Room of Requirement to retrieve it. They are ambushed by Draco Malfoy, Vincent Crabbe, and Gregory Goyle. In the ensuing fight, Crabbe casts Fiendfyre, a powerful and uncontrollable cursed fire. The Fiendfyre consumes the room and everything in it, including the diadem, thus destroying the Horcrux within.

• In the film adaptation of Harry Potter and the Deathly Hallows – Part 2, the diadem's destruction is altered. Hermione Granger gives Harry Potter a Basilisk fang she retrieved from the Chamber of Secrets. Harry stabs the diadem with the fang, and Ron Weasley then kicks it into the Fiendfyre erupting from the Room of Requirement. In the book, the Fiendfyre alone is sufficient to destroy the Horcrux. (film)