Horcrux
A Horcrux is a powerful object in which a Dark wizard or witch has hidden a fragment of his or her soul for the purpose of attaining immortality. Creating one Horcrux gives one the ability to resurrect oneself if the body is destroyed; the more horcruxes one creates, the closer one is to true immortality. Creating multiple Horcruxes is suggested to be costly to the creator, by both diminishing their humanity and even physically disfiguring them.