The Summoning: Impure World Reincarnation binds the soul of a deceased person to a living vessel, restoring them as they were when they were alive in order to do their summoner's bidding. It was originally created by Tobirama Senju, after which he declared it a kinjutsu. Orochimaru rediscovers the technique decades later and improved on the original design, to which Kabuto Yakushi nearly perfects it some time after this.