Rinnegan

The is reputed as the most exalted eyes amongst the. It is characterised by its ripple-like pattern, which spreads over the eyeballs, with light purple sclerae and irides.

Background
The Rinnegan was admired as being able to bring forth all ninjutsu. It was 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. The Rinnegan allows the user to perform the Six Paths Technique.

The first person to possess the Rinnegan was the Sage of the Six Paths. 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 originally wielded by the Sage of the Six Paths, re-merging his bloodlines, that of the Senju and Uchiha, can lead to that person awakening this dōjutsu. This was proven when Madara Uchiha later awakened the dōjutsu by infusing Hashirama Senju's DNA into his body; however, it did not manifest until many years later, when he was near death. At some point after this, he would implant his eyes into Nagato — a young boy of Senju lineage. Under the guise of Madara, Obito Uchiha claimed that he was entitled to take the Rinnegan from Nagato's body after his death. He implanted the left Rinnegan into himself, replacing the Sharingan he sacrificed.

When Madara was reincarnated by Kabuto Yakushi to fight the Allied Shinobi Forces, Madara once again gained access to the dōjutsu; he was able to transform his Eternal Mangekyō Sharingan into the Rinnegan at will. 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, he no longer possessed his Rinnegan as he died without his eyes. Black Zetsu attempted to retake the Rinnegan in Obito's left socket, while a White Zetsu clone managed to retrieve the right Rinnegan from where Obito had hidden it and returned it to Madara's previously empty right socket.

Abilities
One who gains the Rinnegan has access to a multitude of abilities. The holder of these eyes has the potential to completely master all five basic nature transformations that form the basis of ninjutsu. It can also decipher more of the Sage of the Six Paths' tablet than the Sharingan and the Mangekyō Sharingan are able to. The Rinnegan also allows its user to summon and control the Demonic Statue of the Outer Path.

One of the Rinnegan's trademark techniques is the Six Paths Technique, which grants the user multiple abilities known as Paths. The Deva Path can be used to attract and repel targets. The Asura Path can clad the user in mechanised armour and grant them various weapons. The Human Path can read minds, at the cost of ripping out the victim's soul. The Animal Path can summon several different creatures. The Preta Path can absorb any chakra-based ninjutsu. The Naraka Path can summon the King of Hell, which can be used for interrogation and restoration.

Finally, the user is granted the Outer Path, which gives the user control over life and death. It can also be used to control tailed beasts in a similar fashion to the Sharingan and Wood Release through the use of chakra chains. The Outer Path grants a shared field of vision between the Rinnegan wielder, their summoned creatures and the Six Paths of Pain, which also sport the Rinnegan. When he was crippled by Hanzō, Nagato developed the Six Paths of Pain, using the Rinnegan and chakra receivers to control six corpses as extensions of himself. By doing so, Nagato could see each body's field of vision simultaneously, coordinating them with extremely precise planning. Nagato could also channel one of the abilities of the Six Paths Technique through each corpse. Obito also applied this technique, though he used reincarnated jinchūriki. Their eyes sported the Sharingan and Rinnegan, in identical fashion to Obito, and their former tailed beasts were temporarily re-sealed inside them, though the Uchiha would not have them use the powers of the Six Paths Technique.

On its own, the Rinnegan allows the user to see chakra, including otherwise hidden barriers, such as the one which surrounded Konohagakure. Unlike the Sharingan or Byakugan, it doesn't seem to be able to see the flow of chakra within individuals, as shown when Naruto Uzumaki had transformed his shadow clones into rubble and Nagato was unable to see them. Futhermore, the Rinnegan's field of vision can be blocked by such things as dust clouds and smoke bombs.

While the powers of the Rinnegan remain intact upon implanting them into a new person, like Nagato and Obito Uchiha, only one who "naturally" manifests the Rinnegan, as in Madara Uchiha's case, is able to switch between the Rinnegan and Eternal Mangekyō Sharingan; otherwise, the Rinnegan is always activated. Despite this, the Rinnegan does not appear to have any considerable affect on one's chakra reserves, as Nagato wielded it for years unhindered, even in his emaciated state.

Trivia

 * 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.
 * 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 the names with Samsaric realms of reincarnation.