Summon: Impure World Resurrection or Edo Tensei — a kinjutsu created by Tobirama Senju and later improved by Orochimaru, and 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 summoner's will. Three components are required to perform it: a DNA sample of the target, a living sacrifice, and a soul residing in the Afterlife.
After activation, the 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 agonizing, and the vessel's personality is completely supplanted by the summoned's chakra. In Tobirama's original version, the souls returned greatly weakened, and only a few bodies could be controlled. Orochimaru improved the power, but Kabuto achieved a true breakthrough: the summoned are nearly 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 replenishes endlessly, and injuries such as severed limbs do not hinder continued combat and soon regenerate 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 unless they were part of the body at the moment of death.
The Impure World Resurrection can only be undone in three ways: extract the soul (for example, with the Dead Demon Consuming Seal), force the summoner to release the technique (often through genjutsu), or give the summoned an emotional closure that breaks the contract. The summoned can also free themselves if they know the release seals, becoming a completely independent immortal.
