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 modern ninjutsu. 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 down 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 the chakra of his two sons, Indra and Asura, in one's body can lead to that person awakening this dōjutsu. This was proven when Madara Uchiha, Indra's reincarnation at the time, later awakened the dōjutsu from his Mangekyō Sharingan by infusing the DNA of Hashirama Senju, Asura's reincarnation at the time, into his body; however, it did not manifest until many years later when he was near death. At some point after this, Madara would implant his eyes into Nagato — a young boy of Senju lineage. Under the guise of Madara and inheriting the former's work, Obito Uchiha claimed that he was entitled to take the Rinnegan from Nagato's body after his death. He then implanted the left Rinnegan into himself, replacing the Sharingan he sacrificed. and hid the right Rinnegan since he couldn't handle the power of both eyes.

When Madara was reincarnated by Kabuto Yakushi to fight the Allied Shinobi Forces, Madara once again gained access to the dōjutsu. 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 eyes as his reincarnated state had but a reflection of his former self due to him dying without his actual eyes. A White Zetsu clone managed to retrieve the right Rinnegan and returned it to Madara's previously empty right socket.

After receiving half of Hagoromo's power, Sasuke's left eye transformed into the Rinnegan. Unlike the normal Rinnegan, Sasuke's version has the typical concentric circles, but the rings have three tomoe each, reminiscent of his Sharingan, and also has a red sclerae and irides, unlike the standard Rinnegan, which is purple.

Abilities
One who gains the Rinnegan has access to a multitude of abilities, such as the potential to master all five basic nature transformations, and the capacity to use any technique. The Rinnegan allows the user to see chakra, including the chakra points within the body,  as well as things that would otherwise be invisible such as barriers, and the corporeal shadow cast by the Limbo: Border Jail technique. However, the Rinnegan's field of vision can be blocked by simple means such as smoke bombs. The dōjutsu can also completely decipher the Sage of the Six Paths' tablet, unlike the Sharingan and Mangekyō Sharingan. A noteworthy power of the Rinnegan is the ability to summon and control the Demonic Statue of the Outer Path, though this cannot be done using a Rinnegan created through Summoning: Impure World Reincarnation. The Rinnegan also has the power to seemingly teleport targets. This ability is limited to a certain area of effect around the user.

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 various 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 them control over life and death. It also allows the user to manifest chakra chains, which can be used to bind and control tailed beasts in a similar fashion to the Sharingan and Wood Release. The Outer Path grants a shared field of vision between the Rinnegan wielder, the King of Hell, the creatures summoned through the Animal Path and reanimated corpses, which all have the user's Rinnegan reflected in their respective eyes. The user can also manifest chakra receivers. By embedding six corpses with chakra receivers, Nagato developed the Six Paths of Pain technique, a means of controlling the corpses as extensions of himself. Due to sharing his field of vision with the corpses, Nagato could coordinate them with extremely precise planning. He was also able to 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 bound to their bodies using chakra receivers while remaining in Obito's possession through the Demonic Statue. Obito did not have his Six Paths of Pain use the powers of the Six Paths Technique, both to conserve his chakra and because his enemies were already aware of them.

The various abilities of Rinnegan remain intact upon being transplanted into another individual, but only when both eyes are wielded by the original owner can the full power of the Rinnegan be accessed. Also, only Madara, who was an original owner of this dōjutsu, has demonstrated the ability to change his Rinnegan into its Mangekyō Sharingan form and back at will. Despite manifesting his own Rinnegan, Sasuke appears unable to return his Rinnegan into its Mangekyō Sharingan, instead shutting his left eye when not using it. Regardless, the Rinnegan does not appear to have any noticeable effect on one's chakra reserves, as Nagato wielded it for years unhindered, even in his emaciated state and before he was trained as a shinobi.

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.