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Harry Potter speaks with Griphook the Goblin about breaking into Bellatrix Lestrange's vault at Gringotts bank, suspecting that a Horcrux may be hidden there. Griphook agrees to take Harry, Ron, and Hermione to the vault in exchange for the Goblin-made Sword of Gryffindor. Harry asks Ollivander, the wandmaker, to identify two wands they took from Malfoy Manor. Ollivander says they belonged to Bellatrix and Draco Malfoy, but Malfoy's wand has changed its allegiance to Harry.
At Bellatrix's vault, Harry discovers that the Horcrux is Helga Hufflepuff's Cup. He obtains the cup but Griphook takes the sword and abandons the trio, leaving them cornered by the alerted security. However, the three release the dragon guardian of the vault and escape. Harry has a vision of Lord Voldemort killing Goblins, including Griphook, and learns that the Dark Lord has discovered the theft. The sword vanishes from Griphook's hand. Voldemort keeps Nagini, one of his Horcruxes, close to him for protection. Harry also learns there is a Horcrux at Hogwarts, in some way related to Rowena Ravenclaw. The trio apparate into Hogsmeade, which sets off an alarm. They are rescued by Aberforth Dumbledore, who instructs a portrait of his younger sister, Ariana, to fetch Neville Longbottom who leads the trio through a secret passageway into Hogwarts.
Headmaster Severus Snape hears of Harry's return and informs staff and students of the severe punishment for aiding Harry. Harry confronts Snape, who flees after Minerva McGonagall challenges him to a duel. McGonagall gathers the community of Hogwarts to prepare for battle. Luna Lovegood urges Harry to speak to Helena Ravenclaw, who reveals that Voldemort performed "dark magic" on her mother's diadem, which is hidden in the Room of Requirement. Ron and Hermione go to the Chamber of Secrets, where Hermione destroys the Horcrux cup with a Basilisk fang. In the Room of Requirement, Draco Malfoy, Gregory Goyle and Blaise Zabini attack Harry, but Ron and Hermione intervene. Goyle casts a Fiendfyre curse and dies in the uncontrolled flames, but Malfoy and Zabini are saved by the trio before destroying the Ravenclaw diadem. As the school is attacked by Voldemort's forces, the three search for Nagini and head for the boathouse. They witness Voldemort telling Snape that the Elder Wand cannot serve him until Snape dies; he orders Nagini to kill Snape. Before dying, Snape tells Harry to take his memories to the Pensieve.
