Summoning: Impure World Reincarnation

The Summoning: Impure World Resurrection is a forbidden technique used to revive the dead. It was originally developed by Tobirama Senju, who classified it as kinjutsu and never completed it, and later completed by Orochimaru. Kabuto now claims to have mastered it to a degree even higher than them. Kabuto also claims this jutsu to be the "greatest, most powerful technique in the shinobi universe", as it poses no risk at all to the user.

Conditions
To perform this technique, the user must first acquire some of the DNA of the person they intend to revive. Kabuto remarks that this basically amounts to grave-robbing, although blood stains or organs salvaged after the target's death also work. The soul of the intended revived must also reside in the ; those whose soul has been consumed by the Death God, for example, cannot be resurrected. Next, a living sacrifice is required for the soul of the resurrected to use as a vessel.

Once all prerequisites for the technique have been met, the physical remains acquired are smeared on a special scroll and once the scroll is activated, the remains spread out in the form of a special symbol with the living sacrifice in the center of the symbol. Then dust and ash encases the sacrifice's body, giving them the same appearance that the revived had at the time of their death. The person is then revived and the end product is usually stored in a casket until summoned by the user. The user can theoretically revive a limitless number of people in this way, so long as they have enough sacrifices, chakra and DNA to perform the technique.

Summoning
When first summoned, the body of the resurrected is stored in a coffin; their body will appear gray and in a state of minor decay, marred by cracks and other imperfections, and the individual will also appear to be asleep. Upon awakening they retain their personality, memories, and all abilities they had in life, including kekkei genkai, but it does not seem to be able to recreate unique weapons such as Samehada. The summoned can be recalled at will by the user, causing an empty coffin to emerge and reclaim the individual, and the summoner can also use revived individuals to remotely summon coffins containing additional reinforcements.

Control
After the individual has been summoned and awakened, the summoner can bind the individual to his or her will by using a special talisman, which is attached to the end of a kunai and implanted in the brain. Upon implanting the talisman, the resurrected individual will regenerate further, eliminating any remaining imperfections and restoring color to their bodies and clothing. Kabuto either remotely controls or tracks the summoned individuals using pebbles he manipulates on a simple grid, which acts as a map.

Different talismans can be used to enact different degrees of control. Orochimaru's talismans completely eliminated the personalities of the summoned, turning them into mindless killing machines under his command. Kabuto prefers to use a weaker binding talisman on certain individuals, allowing them to retain some degree of their own personality. The latter method is useful for psychological warfare, and can also allow the summoned individual to tap into their own emotions, memories, or creativity to enhance their effectiveness in combat, but also carries a host of drawbacks: it takes more effort to retain control the weaker the binding is, and if the binding is too weak, it's possible for their hearts to be swayed by strong emotions, which can result in the soul breaking free and returning to the Pure World. After gaining more experience with the technique, and absorbing Orochimaru's chakra from Anko Mitarashi, Kabuto exerts greater control over the summoned and even overwrites his own talismans, greatly increasing the power of the binding.

Countering
The revived are impossible to kill by normal means. Any damage they receive will regenerate, be it lost limbs or complete disintegration. Not even killing the summoner will get rid of them. There are only three known methods to defeat the technique:
 * 1) Seal away the soul of the revived individual.
 * 2) Have the summoner end the technique. As they are unlikely to do this voluntarily, using a genjutsu to trick them into canceling the technique is ideal. The sequence of hand seals for canceling the technique is Dog → Horse → Tiger and saying.
 * 3) The revived individual is affected in some emotional way that gives them closure; Kankurō notes that human emotions are not so easily restrained. However, this method cannot work if the summoner destroys the personality of the revived individual before their soul is freed of its bonds.

Once any of these methods is accomplished, the bodies will crumble into dust, with the bodies of the sacrificed individual lying among the ashes.

Trivia

 * In chapter 117 of the manga, when Orochimaru performs the technique, Hiruzen anticipates the summoning of a third coffin; when a third coffin is not summoned, he's surprised and assumes that the summoning technique failed. Years later, in chapter 520, Kabuto explains that Orochimaru's attempt to summon the Fourth Hokage had failed due to his soul not residing in the "pure world". This results in a contradiction in the anime version of events: in episode 69 of the anime, when Orochimaru used this jutsu, three coffins were summoned, with "four" (四, Yon) written on the third; though the summoning of the Fourth Hokage still fails, the actual failure would have occurred when Orochimaru preformed the original preparatory ritual, and thus the summoning of a third coffin would have been pointless.
 * When Kabuto first approached Madara about joining forces, he summoned Deidara, Itachi, Kakuzu, Nagato, and Sasori as a demonstration of power. When Madara threatened to refuse Kabuto's offer, Kabuto summoned a sixth casket that compelled Madara to not only join forces with Kabuto, but to call him a "Madman!". The contents of the sixth casket were obscured.
 * The video game, Naruto: Ultimate Ninja 2, the (non-canon) storyline contradicts the idea the soul of the revived must reside in the Pure World, as Orochimaru revives the Third Hokage no differently than anyone else he summons in the game.