Outer Path — Samsara of Heavenly Life Technique

By channelling his power through the King of Hell, the Rinnegan wielder can re-infuse new life force energy to the bodies of those who have died. With their rejuvenated bodies acting as an anchor, the individual souls are then able to leave even the crossroad between life and the afterlife, returning back to their physical vessels. The technique targets all the individuals killed, even those not necessarily killed by user. This technique seemingly requires a massive amount of chakra, as Konan feared the worst for Nagato when he used it after having previously expended so much chakra. Nagato also became severely weakened, his hair became increasingly thinner and greyer as he performed the technique.

Influences
As with many of Nagato's techniques, it is influenced by Buddhist terminology. , derived from the Sanskrit Tīrthika, refers to any doctrine which "treads the outer path" to enlightenment. This is opposed to the teachings of orthodox Buddhism, the, and is thus considered misguided and heretical.

Trivia

 * While Obito Uchiha noted to Zetsu that this technique was originally meant to be used for his purposes, but in reality it was supposed to be used to revive Madara Uchiha. Madara would have eventually reincarnated anyway and expressed surprise and disappointment that his return didn't go as planned, as a reincarnated corpse cannot become a jinchūriki.
 * After he took Nagato's Rinnegan and trasplanted it in his left eye socket, Obito has been noted to be able to use this technique, though it is hinted that he would die if he were to use it, even for resurrecting only one person, in his case Madara.