Outer Path — Samsara of Heavenly Life Technique

By channelling their 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 the 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. This technique results in the death of the user regardless of whether or not they're not on the peak of their power when performing this technique as stated by Obito.

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

 * Madara Uchiha — and Obito under the guise of Madara — noted that this technique was supposed to be used to revive him. Madara would have eventually reincarnated anyway and expressed surprise and disappointment that his return didn't go as planned, as only a living body can become a jinchūriki, which he wanted to do with the Ten-Tails.
 * Because Madara has been resurrected and not revived, he needs Obito to perform this technique so that he can become the Ten-Tails' jinchūriki. Obito has noted that this would result in his own death, however.