Hufflepuff's Cup

Helga Hufflepuff's Cup was a magical item created by one of the founders of Hogwarts School of Witchcraft and Wizardry, Helga Hufflepuff. It was a small golden cup with two finely-wrought handles with a badger engraved on the side. The badger is the symbol of Hufflepuff House.

Creation
The cup was a creation of Helga Hufflepuff, the celebrated Founder of Hufflepuff House. It was described as a shining golden cup with two finely wrought handles on either side and a badger engraved on it's surface. The cup was said to possess many magical powers, though the exact nature of those powers is not known. Hufflepuff was brilliant with food-related charms and with house-elves, so the cup may have been the very first dining utensil at Hogwarts to assist in the magical transportation of food from the House-Elf Kitchens. The cup remained with Hufflepuff until the time of her death.

Horcrux Transformation
The cup was passed down through the Hufflepuff family, and through the centuries made its way to Hepzibah Smith, a descendant who kept the cup as a priceless heirloom. Around 1946, Smith showed the cup to Tom Marvolo Riddle, who was at that time employed at Borgin and Burkes. She dazzled Riddle with the cup and fondly stated she could never part with it. Along with the cup, Smith possessed Salazar Slytherin's Locket.

Smith was found dead two days later. Her elderly house-elf, Hokey, recalled mistakenly putting poison in Smith's cocoa, however, the truth was that Riddle had imbedded a false memory in Hokey as he himself had murdered Smith for the artifacts. Riddle fled with the cup and the locket. Smith's family realized the cup and the locket were missing shortly after her death, but by that time Riddle had resigned his post at Borgin and Burkes. Riddle was neither seen nor heard of for a decade.

Riddle, or Lord Voldemort as he was referred to at that point, used the cup transformed the cup into a Horcrux, using Smith's murder as a tool, and left it in the care of his trusted Death Eater, Bellatrix Lestrange. Not knowing that the cup was then a Horcrux, Lestrange stored it in her family vault at Gringotts Wizarding Bank. It was protected there by a spell which would cause any object to multiply exponentially if touched by anyone other than the vault's owners. In addition to this, a further protective charm was placed on the vault to cause the objects to glow hot as fire and burn the flesh of anyone trying to remove them without authorization.

Search to Reclaim the Cup
Years later, Albus Dumbledore and Harry Potter theorized that Lord Voldemort had chosen Hufflepuff's Cup as an object for one of his Horcruxes. After an arduous search, Harry obtained critical information that correctly identified the Lestrange vault as the hiding place for a Horcrux. Harry, Ron Weasley, Hermione Granger, and the goblin Griphook infiltrated Gringotts using Polyjuice Potion. They managed to narrowly bypass the vault's securities before fleeing Gringotts on one of the bank's dragons.

Griphook betrayed the trio and claimed Godric Gryffindor's sword as his own after their escape. As the only readily available means to destroy a Horcrux at that time was through the use of the sword, Hermione and Ron were forced to venture into the Chamber of Secrets to retrieve Basilisk fangs, which they used to destroy the cup.