Salazar Slytherin's Locket

• Type: Horcrux, Heirloom of Salazar Slytherin
• Owners: Salazar Slytherin, the Gaunt family (including Merope Gaunt), Caractacus Burke, Hepzibah Smith, Tom Riddle (Lord Voldemort), Kreacher, Mundungus Fletcher, Dolores Umbridge, Harry Potter, Ron Weasley
• Maker: The locket was likely crafted by or for Salazar Slytherin. It was turned into a Horcrux by Lord Voldemort.

The locket is described as a heavy, oval-shaped container made of gold. Its most distinctive feature is a serpentine 'S' mark on its cover, inlaid with small, glittering green stones. The locket was capable of being opened, though when shown to Tom Riddle by Hepzibah Smith, it was empty. After Lord Voldemort transformed it into a Horcrux, it became impossible to open through ordinary means or simple spells. It could only be opened by a speaker of Parseltongue.

As one of Lord Voldemort's Horcruxes, the locket contained a fragment of his soul, granting him a form of immortality. The portion of soul within endowed the locket with a malevolent sentience and several powerful defensive capabilities.

• Corrupting Influence: The locket exerts a powerful negative influence on anyone who wears or carries it for an extended period. It amplifies negative emotions such as anger, suspicion, and despair. This was seen when Harry Potter, Ron Weasley, and Hermione Granger took turns wearing it; it made them irritable and prone to arguments, most notably causing Ron to feel intensely jealous and inadequate, leading to his temporary departure from the group.
• Defensive Enchantments: The locket is extremely durable and resistant to most forms of magical damage. Spells such as the Severing Charm (`Diffindo`) simply bounced off its surface. It was immune to Fiendfyre when cast by an inexperienced wizard like Vincent Crabbe. Destruction of a Horcrux requires the container to be damaged beyond any magical repair.
• Self-Defense: The locket could actively defend itself. When Harry attempted to retrieve the Sword of Gryffindor from a frozen pond, the locket tried to strangle him. When opened with Parseltongue for destruction, the soul fragment within manifested as ghostly apparitions of Tom Riddle that taunted Ron Weasley with his deepest fears and insecurities.
• Destruction: The locket could only be destroyed by a substance of immense destructive power, such as Basilisk venom or Fiendfyre. It was ultimately destroyed by Ron Weasley using the Sword of Gryffindor, which had been imbued with Basilisk venom.

The locket was a priceless heirloom belonging to Salazar Slytherin, one of the four founders of Hogwarts. It was passed down through his direct descendants, the Gaunt family. The last of the Gaunts to own it was Merope Gaunt, Lord Voldemort's mother. In a state of desperation after being abandoned by her husband, Tom Riddle Sr., Merope sold the locket to Caractacus Burke at Borgin and Burkes for a mere ten Galleons. Hepzibah Smith, a wealthy but foolish collector, later purchased the locket from Burke. The young Tom Riddle, then working at Borgin and Burkes, visited Hepzibah and charmed her into showing him her two greatest treasures: the locket and Hufflepuff's Cup. Days later, Riddle murdered Hepzibah, stole both items, and magically altered the memory of her house-elf, Hokey, to take the blame. Riddle later used the murder of a Muggle tramp to turn the locket into his third Horcrux. Voldemort hid the locket in a secret seaside cave from his childhood, placing it within a basin of poison on an island in an underground lake, protected by numerous powerful enchantments, including a blood-toll entryway and an army of Inferi. However, his Death Eater, Regulus Black, learned of the Horcrux and turned against him. Accompanied by his house-elf Kreacher, Regulus overcame the cave's defenses. He drank the potion himself, ordering Kreacher to swap the real locket with a fake one and to destroy the original. Regulus was killed by the Inferi, and Kreacher, despite his best efforts, was unable to destroy the powerful object. The locket remained hidden at Number Twelve, Grimmauld Place until it was stolen by Mundungus Fletcher. To avoid prosecution for unlicensed peddling, Mundungus gave the locket as a bribe to Dolores Umbridge. She wore it at the Ministry of Magic, falsely claiming the 'S' stood for Selwyn, a pure-blood family to which she pretended to be related. After learning of its whereabouts, Harry Potter, Ron Weasley, and Hermione Granger infiltrated the Ministry of Magic and successfully stole the locket from Umbridge. They spent months carrying the cursed object until they discovered that the Sword of Gryffindor could destroy it. In the Forest of Dean, Ron used the sword to destroy the locket after Harry opened it by speaking Parseltongue.

The locket is a central plot device in the latter half of the series, representing Voldemort's pride in his Slytherin heritage and his fear of death. The quest to find and destroy it drives the narrative of Harry Potter and the Deathly Hallows, leading the main characters to locations like the Ministry of Magic and testing their friendship to its limits. Its destruction by Ron Weasley is a pivotal moment of character development for him, proving his courage and loyalty and marking a major victory in the war against Lord Voldemort. The fake locket, containing the note from R.A.B., serves as the key cliffhanger at the end of Harry Potter and the Half-Blood Prince, initiating the hunt for the real Horcruxes.

• In the film adaptation of Harry Potter and the Half-Blood Prince, the locket retrieved from the cave by Harry Potter and Albus Dumbledore is shown to be the fake one containing the note from R.A.B.. (film)
• The film depiction of the locket's destruction includes dark, smoke-like figures of Harry and Hermione emerging from it to taunt Ron, a visualization of the fears the locket preys upon. (film)