Rinnegan

The is reputed as the most exalted eyes amongst the, along with the Byakugan and the Sharingan. It originated from Kaguya Ōtsutsuki's Rinne Sharingan, and truly manifested for the first time as a kekkei mōra in her son, the Sage of the Six Paths. Its dual variant is characterised by a ripple-like pattern which spreads over the eyeball, with light purple sclerae and irides, and its singular variant has the same features, albeit containing a pattern of six tomoe.

Background
It is said that in times when the world is in disorder, a person is sent down from the heavens to become either a "God of Creation" who will calm the world, or a "Destroyer" who will reduce everything to nothingness. While its predecessor, the Rinne Sharingan, was wielded by Kaguya Ōtsutsuki, the Rinnegan itself was first manifested by her son, Hagoromo Ōtsutsuki, who came to be revered as the Sage of the Six Paths by creating the groundwork that brought forth all modern ninjutsu. As a result of the Sage's mythical status, many people believed the Rinnegan was only a legend or a mutation.

Because the Rinnegan was wielded by the Sage of the Six Paths, it is possible to awaken the dōjutsu by combining the chakra of his two sons, Indra Ōtsutsuki and Asura Ōtsutsuki, thus bringing forth the Sage's own chakra. Black Zetsu spent centuries manipulating the reincarnations of Indra and Asura in an attempt to make one of them awaken the Rinnegan through this method, but only Madara Uchiha was successful in this endeavor. Madara, Indra's reincarnation at the time, awakened the dōjutsu by infusing the DNA of Hashirama Senju, Asura's reincarnation at the time, into his own body; however, it did not awaken until many years later, when his natural lifespan was coming to its end. At some point after this, Madara implanted his eyes into Nagato — a young boy of Senju lineage. Under the guise of Madara, Obito Uchiha later claimed that he was entitled to take the Rinnegan from Nagato's body after his death. He implanted the left Rinnegan into himself and hid the right Rinnegan, unable to handle the power of both eyes.

When Madara was reincarnated by Kabuto Yakushi, who once again implanted Hashirama's DNA into his body, he gained access to the Rinnegan once more. Based on data collected over the years, Orochimaru and Kabuto theorised that because the Sharingan originated from the Rinnegan, it was possible for the dōjutsu to change into the Rinnegan as part of a "natural evolution". However, upon Madara's true revival as a living being, his artificially-created Rinnegan crumbled into dust, rendering him blind. A White Zetsu managed to retrieve the right Rinnegan from Obito's hiding place and returned it to Madara, who implanted it in his previously empty right eye socket. After becoming the Ten-Tails' jinchūriki, Madara obtained the left Rinnegan from Black Zetsu, who had taken over Obito's body, and awakened a Rinne Sharingan on his forehead by approaching the moon.

After receiving half of Hagoromo's power, Sasuke Uchiha awakened a Rinnegan containing six tomoe in his left eye.

Abilities
One who possesses the Rinnegan has the capacity to master any technique and the unprecedented ability to completely master all five elemental nature transformations. The Rinnegan is able to see chakra, including the Eight Gates within the body, as well as otherwise invisible barriers. However, as seen with Nagato's usage, the dōjutsu's field of vision can be blocked by simple means such as smoke bombs. The Rinnegan can completely decipher the Sage of the Six Paths' tablet, which the Sharingan and Mangekyō Sharingan can only partially interpret. It also grants the ability to summon and control the Demonic Statue of the Outer Path, though this cannot be done using an artificial Rinnegan.

The Rinnegan grants the user six abilities which are collectively known as the Six Paths Technique. The Deva Path can attract and repel targets; the Asura Path can integrate mechanical armour and weaponry into the user's body; the Human Path can read a person's mind at the cost of extracting their soul; the Animal Path can summon creatures which sport copies of the user's Rinnegan; the Preta Path can absorb chakra in any form; and the Naraka Path can summon the King of Hell for the purpose of interrogation or restoration.

The user gains the ability to create the Rinnegan's trademark black receivers, to which they can transmit their chakra across long distances. By embedding up to six corpses with chakra receivers, the user can control them as additional bodies, referred to as the Six Paths of Pain. Each Pain possesses copies of the user's dōjutsu, the ability to create additional chakra receivers, and one of the powers of the Six Paths Technique. The user shares their field of vision with the Six Paths of Pain, as well as the King of Hell and the creatures summoned through the Animal Path. The user is considered the seventh Pain, the Outer Path, and is said to preside outside of live and death, granting them the power to revive the dead in exchange for their own life. The Outer Path also allows the user to bind those who touch their chakra receivers and manifest the chakra chains of the Demonic Statue.

With this dōjutsu, Madara could perform the Limbo: Border Jail technique, creating corporeal shadows which are only visible to the Rinnegan. Sasuke's Rinnegan allows him to shift spaces within a certain range of himself. Sasuke's Rinnegan also retains his left Sharingan's powers, including usage of Amaterasu, and the ability to cast powerful genjutsu, with which he was able to control all nine tailed beasts at once. Conversely, Madara's wood clone reverted his Rinnegan to its Eternal Mangekyō Sharingan form in order to cast genjutsu.

The various abilities of the Rinnegan remain intact upon being transplanted into another individual, but only when both eyes are wielded by the original owner can their full power be accessed, at least in the case of Madara's eyes. Also, only original owners of this dōjutsu have demonstrated the ability to deactivate it. Because of its ocular power and potent chakra, not all individuals are capable of handling the Rinnegan and risk "losing themselves" by transplanting one, a trait which is worsened by attempting to implant two. It is unknown what effect this dōjutsu has on one's chakra reserves, though Nagato wielded two transplanted Rinnegan for years without displaying any adverse effects to his stamina.

Trivia

 * is the Japanese term for Samsara, the cycle of reincarnation or rebirth in several Indian religions. This is reflected in the names of all Six Paths of Pain, which share their names with the six Samsaric realms of reincarnation.
 * The kanji is also used in Sharingan and Rinne Sharingan, potentially linking the three terms etymologically.
 * In the event that a person's Sharingan was blinded prior to awakening the Rinnegan, said blindness is apparently negated by the dōjutsu's initial activation.
 * In the anime, the Rinnegan was depicted as being multicoloured in its first few appearances. Once coloured manga illustrations of the Rinnegan were released, this was corrected. However, whereas the Rinnegan is depicted as a single shade of purple in the manga, the centre-most ring is depicted as a darker purple in the anime.
 * In Naruto: Shippūden episode 203, a silhouette of the Sage of the Six Paths is shown. Here, the Sage's Rinnegan is shown to be red instead of the usual colour.
 * In the digital manga chapters colourised by Shueisha's production team, Sasuke's Rinnegan was coloured red, like Madara and Kaguya's Rinne Sharingan. Later illustrations coloured by Kishimoto instead depict it with the usual purple colouring. The colouration was corrected in subsequent digitally colourised chapters.
 * In the anime, the Rinnegan appears to grant its user the ability to levitate to some extent.