A Horcrux is a fictional magical object in the Harry Potter series by J. K. Rowling. It is a Dark Magic device created for the purposes of attaining immortality. The concept is first introduced in the sixth novel, Harry Potter and the Half-Blood Prince, though Horcruxes are present in earlier novels without being identified as such. Rowling uses the character Horace Slughorn to introduce their properties. The retrieval and destruction of Lord Voldemort's Horcruxes forms the main focus of the final two books in the series, Harry Potter and the Half-Blood Prince and Harry Potter and the Deathly Hallows.
In an online diary entry, Rowling described a Horcrux as a "receptacle in which a Dark wizard has hidden a part of his soul for the purposes of attaining immortality." With part of a wizard's soul thus stored, the wizard becomes immortal so long as the Horcrux remains intact. For this reason, Horcruxes are typically hidden in a safe location. Even if the wizard's body is destroyed, a portion of his soul will remain preserved within the Horcrux. However, the destruction of the creator's body leaves the wizard or witch in a state of half-life, without corporeal form. The dark magic involved in the creation of a Horcrux is considered most despicable and is therefore rarely published, even in books devoted to the Dark Arts.A Horcrux can be made from any normal object, including living organisms. Destroying a Horcrux will destroy the fragment of soul contained within it, ending its protection and returning the creator to a state of mortality. If a wizard has created more than one Horcrux, he will remain immortal until all are destroyed. Once destroyed, the wizard will die normally if mortally wounded. The portion of soul within a Horcrux also has the ability to take spiritual possession of other people. This possession is limited to those who become emotionally attached to the Horcrux. Once possessed, the soul within the Horcrux can take total control of the person's actions while the person remains completely unaware of the connection. Once a person has become possessed by a Horcrux, the Dark Wizard has the ability to take corporeal form by draining the life force of the possessed person. None of these spiritual connections extend to a wizard's other Horcruxes. The portions of soul also possess some level of sensory awareness, being able to sense when in danger and defend themselves.Lord Voldemort is the only wizard explicitly mentioned as having created a Horcrux (though others are known to have done so), and is the only wizard known to have created more than one. In a recent interview J.K. Rowling mentioned that Herpo the Foul, parselmouth and first breeder of a basilisk, created the first Horcrux.