Outer Path — Samsara of Heavenly Life Technique

By channelling all of their chakra 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 either all the individuals recently killed, or a single person from long ago.

This technique can also be used on people brought back to life using Summoning: Impure World Reincarnation, transforming the debris and ash that forms the corpse vessel into a real body of living flesh and blood; even if they have been dead for many years. However, they would be revived to the state they were in prior to their death. Madara, for example, did not have his original eyes upon him during his passing and was resurrected without them.

This technique seemingly requires a massive amount of chakra, risking death in the process, as Konan feared the worst for Nagato when he used it after having previously expended so much chakra. After using the technique, Nagato became severely weakened; his hair became white due to overexertion of his chakra. Obito's usage of the technique (even on a single target, as opposed to Nagato's use on a village's population) brought him to his inevitable death, as Black Zetsu noted.

Influences
As with many of the Rinnegan'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 eventually be 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. Eventually, Madara successfully forced Obito to perform the technique.
 * Because Madara has been reincarnated 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. Due to Obito's usage of the technique being interrupted and incomplete, he was critically drained and his hair whitened, though he lived to become the Ten-Tails' jinchūriki.
 * When written as '輪廻転生', Rinne Tensei means "the circle of transmigration".
 * Noticeably, despite the fact that Madara was simply using another person's corpse when he was revived by Obito, Madara still retained his physical appearance despite his body belonging to someone else who had an entirely different appearance than him. It seems that this technique does not need the original body for the owner to be brought back, as Madara's original plan consisted of Obito reviving him at a time where the original body would have decomposed.