This locket was an heirloom of the Black family. With the help of his House-elf Kreacher, Regulus swapped it for Salazar Slytherin's Locket, which was hidden in the seaside cave, in an attempt to destroy Voldemort's Horcrux and bring down the Dark Lord. Regulus was killed in the process when he was dragged underwater by the Inferi, but Kreacher was successfully able to switch the lockets and escape. Regulus' locket was found by Harry Potter and Albus Dumbledore in June of 1997 when they also attempted to obtain the Horcrux. Harry gave it to Kreacher the following August, as an act of kindness.