Hufflepuff's Cup

Helga Hufflepuff's Cup is an heirloom which belonged to Hepzibah Smith. The cup, created by one of the Hogwarts founders, Helga Hufflepuff, is a small, golden cup with two finely wrought handles and a badger engraved on it. Hepzibah shows the cup to Tom Riddle telling him that it possesses magical properties.

Hepzibah Smith was found dead a few days later: her House elf, Hokey, was accused of poisoning her and Hokey admitted committing the crime. However, Albus Dumbledore believed that Tom Riddle murdered Hepzibah in order to steal the cup and used a memory charm on Hokey to avert suspicion from himself. Hepzibah's family later discovers the cup is missing.

Dumbledore, and later Harry Potter, theorized that Lord Voldemort had turned the cup into a Horcrux. After months of searching, Harry guessed correctly that one of Voldemort's Horcruxes (the cup) was hidden in the vault of Bellatrix Lestrange in Gringotts wizarding bank. Harry and his friends Ron Weasley and Hermione Granger, along with Griphook, a Goblin who worked at Gringotts, broke into the vault using a plan involving Ron and Hermione disguising themselves with Polyjuice Potion and Harry and Griphook hiding under Harry's Invisibility Cloak. Eventually the group made their way to Bellatrix's vault, despite the fact that the bank's enchantments had ruined their disguises. Once inside, the party discovered that any object inside the vault would multiply exponentially if touched by anyone other than the vault's owners. Before they were trapped inside the vault by the multiplying treasure, Harry, Ron and Hermione retrieved the cup and escaped by climbing onto the back of a dragon that guarded other Gringotts vaults.

The mission was not without a cost, however, as Griphook betrayed the trio and stole the sword of Godric Gryffindor. This was a huge setback as the only way they had discovered to destroy a Horcrux was by using Basilisk venom, which the sword had been imbued with.

Harry, Ron and Hermione kept the Horcrux with them until they could find a way to destroy it. After returning to Hogwart's, Ron realized that the remains of the Basilisk Harry had fought in his second year was still in the Chamber of Secrets. Ron brought Hermione to the Chamber of Secrets, where they removed the fangs from the Basilisk to use as weapons to destroy the remaining Horcruxes. Hermione then stabbed the cup with a fang to destroy it once and for all.