Summoning: Impure World Resurrection is a kinjutsu created by Tobirama Senju and later improved by Orochimaru, then nearly perfected by Kabuto Yakushi. The technique binds the soul of the deceased to a living vessel, restoring the body to the state it was in at the last moments of life, and forcing the summoned to serve the will of the summoner. Three components are required: a DNA sample of the target, a living sacrifice, and a soul residing in the Afterlife.
After activation, genetic material is applied to a special scroll, and a ritual seal forms around the sacrifice. The victim's body is covered in ash and dust, taking on the appearance of the resurrected; the process is painful, and the vessel's personality is completely displaced by the summoned's chakra. In Tobirama's original execution, the souls returned greatly weakened, and only a few bodies could be controlled. Orochimaru improved the power, but the true breakthrough was achieved by Kabuto: the summoned are almost equal to their living selves in strength, and the number simultaneously controlled is limited only by available sacrifices and the user's own power. This turns the technique into the ultimate weapon.
Control is exercised through a talisman implanted in the brain. At a low level of control, the summoned retains their personality and tactical freedom but must obey. At the highest level, the personality is erased, and every movement is dictated directly, which limits multitasking. The summoned possess an immortal body: any wounds regenerate, chakra is replenished infinitely, and damage such as severed limbs does not hinder continued combat and soon regenerates just the same. At the same time, memories of life, kekkei genkai, and all mastered techniques are preserved. The technique does not reproduce illnesses and does not return foreign fragments if they were not part of the body at the time of death.
The Impure World Resurrection can only be canceled in three ways: extracting the soul (e.g., with the Dead Demon Consuming Seal), forcing the summoner to release the technique (often through genjutsu), or giving the summoned emotional closure that breaks the contract. The summoned can also free themselves if they know the release seals, becoming completely independent immortals.
