In Harry Potter and the Deathly Hallows, which object destroys Helga Hufflepuff’s cup Horcrux?

In Harry Potter and the Deathly Hallows, a basilisk’s fang destroys Helga Hufflepuff’s cup Horcrux.

Harry, Ron, and Hermione break into the Chamber of Secrets to destroy the cup, which Voldemort used as one of his Horcruxes. Ron retrieves a basilisk fang from the remains of the giant serpent killed by Harry in the second book. Hermione then drives the fang through the cup, destroying the soul fragment inside it.

Basilisk venom is one of the rare substances powerful enough to destroy a Horcrux. The Sword of Gryffindor can also destroy Horcruxes because it absorbed basilisk venom when Harry used it to kill the basilisk. However, the sword is not the object used against Hufflepuff’s cup.

This detail is often confused with the destruction of Tom Riddle’s diary, which Harry destroys with a basilisk fang in Chamber of Secrets. The cup is destroyed later, during the trio’s return to Hogwarts.