R.A.B. Locket

• Type: Magical Object, Locket, Fake Horcrux
• Owners: Regulus Arcturus Black, Albus Dumbledore (briefly), Harry Potter (briefly)
• Maker: Unknown

The R.A.B. Locket is an exact replica of Slytherin's Locket, a priceless heirloom and one of Lord Voldemort's Horcruxes. It is described as a heavy, gold locket. Unlike the real Horcrux, it can be opened by normal means. Inside, instead of the Horcrux, it contains a small, folded piece of parchment. This note, written by Regulus Arcturus Black, reads: To the Dark Lord I know I will be dead long before you read this but I want you to know that it was I who discovered your secret. I have stolen the real Horcrux and intend to destroy it as soon as I can. I face death in the hope that when you meet your match, you will be mortal once more. R.A.B.

The R.A.B. Locket has no known magical properties of its own. Its primary and sole purpose was to serve as a decoy, intended to be swapped with Slytherin's Locket to trick Lord Voldemort into believing his Horcrux was still safely protected. The note contained within was its most significant feature, serving as a final testament from Regulus Black and a crucial clue for Harry Potter in his quest to find and destroy all of Voldemort's Horcruxes.

After discovering that Lord Voldemort had created Horcruxes to achieve immortality, Regulus Arcturus Black, a former Death Eater, defected. Deducing that Voldemort had used his family's house-elf, Kreacher, to help hide Slytherin's Locket in a seaside cave, Regulus resolved to retrieve and destroy it. He created or procured this replica locket and took Kreacher with him to the enchanted cave. To reach the real Horcrux, which lay in a basin of Potion of Despair, Regulus drank the potion himself, suffering its terrible effects. In his weakened state, he ordered Kreacher to swap the lockets, placing the replica with the note inside the basin. He then instructed Kreacher to take the real Horcrux and destroy it. Regulus was subsequently dragged to his death by the Inferi guarding the potion. The fake locket remained undisturbed in the basin for nearly two decades. In 1997, Albus Dumbledore and Harry Potter journeyed to the cave, believing they were retrieving the real Horcrux. Dumbledore drank the Potion of Despair, and Harry retrieved the locket from the bottom of the basin. Following Dumbledore's death later that night, a devastated Harry discovered that the locket they had risked so much for was a fake when he found the note from R.A.B. inside. The identity of R.A.B. remained a mystery to Harry until he, Ron Weasley, and Hermione Granger questioned Kreacher at Number Twelve, Grimmauld Place and finally learned the full story of Regulus's sacrifice.

The R.A.B. Locket is a pivotal plot device that serves as the major cliffhanger at the end of Harry Potter and the Half-Blood Prince. Its discovery reveals that Albus Dumbledore's final mission was, on the surface, a failure, and that his sacrifice in the cave was to retrieve a worthless decoy. This revelation provides Harry Potter with his first tangible proof that someone else knew about the Horcruxes and had worked against Voldemort. The note from “R.A.B.” introduces a central mystery that drives the first part of Harry Potter and the Deathly Hallows, leading Harry to uncover the tragic story and heroic redemption of Regulus Arcturus Black. It refocuses Harry's mission, transforming it from a hunt guided by Dumbledore into a detective-like quest of his own.

In the film adaptation of Harry Potter and the Half-Blood Prince, the discovery of the note inside the locket occurs moments after Harry and Dumbledore return to Hogwarts, in the Headmaster's office, rather than later at the Dursleys' house. This change accelerates the reveal for cinematic pacing (film).