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 and a few Jewels. The badger is the symbol of Hufflepuff House. The cup also has the dubious distinction of being the only object known to have been stolen from a vault (specifically the vault of the Lestrange family) at Gringotts Wizarding Bank.

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 its 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. In 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. She kept them well hidden even from her family members.

Smith was found dead two days later. Her elderly house-elf, Hokey, recalled mistakenly putting poison in Smith's cocoa, however, Riddle had embedded a false memory in Hokey as he himself had murdered Smith for the artefacts. 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 called himself at that point, transformed the cup into his fourth Horcrux, using Smith's murder as the tool. Many years later he left it in the care of his trusted Death Eater, Bellatrix Lestrange. Although she did not know that the cup was a Horcrux, Lestrange treated the object with extreme priority, storing it in her family vault at Gringotts Wizarding Bank, considered to be impossible to plunder. In addition to the bank's extensive security measures, 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 curse 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. They did not, however, know where it might be located.

During the hunt for the Horcruxes, Harry, Ron and Hermione were captured by Snatchers and brought to Malfoy Manor, where Bellatrix Lestrange panicked at the sight of Godric Gryffindor's Sword — which she had believed to be in her vault as well — in their possession. She interrogated and tortured Hermione with the Cruciatus Curse demanding to know what else they had taken. This made Harry suspect that Hufflepuff's Cup might be the other item in her vault.

Later, Harry, Hermione and Ron infiltrated Gringotts with the assistance of the goblin Griphook and the use of Polyjuice Potion. As they searched the vault, Harry felt a jolt in his heart when his wand light passed over Helga Hufflepuff's cup, which was kept on a higher level. 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 Hermione used to destroy the Cup.

Behind the scenes

 * Hufflepuff's Cup is neither seen nor mentioned in the film version of Harry Potter and the Half-Blood Prince. Similarly, the hypothetical Horcruxes of Nagini and an unknown artefact of Ravenclaw's are never suggested to Harry by Dumbledore prior to his death. This leaves Harry in a significantly more challenging predicament at the end of the sixth film than in the book, as he has only one lead to follow entering the final film: the original pilfered locket from the Horcrux cave. The clue he received in the film was from Bellatrix, who was in a frantic frenzy when she thought her vault was broken into.
 * In the film, Harry finds the Horcrux by sensing it due to the Horcrux in his head. He is also able to find the diadem this way.
 * In the film the cup is never named; it is only called "The Horcrux" or "The Cup", and its back-story of Helga Hufflepuff owning it goes unmentioned.
 * In the film, when the cup is destroyed, its destruction causes a tsunami to form in the nearby water, and Voldemort's face to appear in the tsunami as the fragment of his soul is released and destroyed.

Appearances

 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Deathly Hallows
 * Harry Potter and the Deathly Hallows: Part 2
 * Harry Potter and the Deathly Hallows: Part 2 (video game)
 * Harry Potter and the Forbidden Journey