The medallion of slytherin
Voldemort's mother inherited the old locket of Salazar Slytherin, but she sold it inBorgins & Burke. Voldemort was able to recover the locket and put it years later in a cave full of Inferi (a kind of zombie). One of his Death Eaters, Regulus Black (Sirius's brother) turned against him and decided to find and destroy his horcruxes.With the help of his house-elf named Kreacher, Regulus took the locket and left afake in place. But Regulus was killed by Inferi, Monster returned to the Black family home and hid the medallion. Years later, he was stolen by Mundungus Fletcher who sold it to Dolores Umbridge. Ron destroyed the locket using the sword ofGryffindor.