Rinnegan

The is reputed as the most exalted eyes amongst the, the others being the Byakugan and the Sharingan. Rinnegan wielders are said to be sent down from the heavens to become either a "God of Creation" who will calm the world's disorder or a "Destroyer" who will reduce everything to nothingness. Rinnegan are characterised by light purple sclerae and irides with a ripple-pattern that spreads over the eyeball, but can have different forms as well.

Acquisition
The Rinnegan was first manifested by Hagoromo Ōtsutsuki, inherited as a kekkei mōra from his mother's Rinne Sharingan. With his Rinnegan he saved the world from the Ten-Tails and created ninshū, the precursor of modern ninjutsu. For his contributions to the world, Hagoromo became revered as the "Sage of the Six Paths" and rose to mythological status through the centuries, with his Rinnegan coming to be deemed by many a legend or a mutation.

The Rinnegan can be awakened by combining the chakra of Hagoromo's sons, Indra and Asura, in order to create Hagoromo's chakra. Black Zetsu spent centuries attempting to do so, trying to manipulate the reincarnations of Indra and Asura to awaken the Rinnegan. It was not until the time of Madara Uchiha - Indra's reincarnation - that Black Zetsu was successful, when Madara infused himself with the DNA of Hashirama Senju - Asura's reincarnation. However, Madara's Sharingan did not become Rinnegan until decades later, at the end of his natural lifespan; this also seemingly restored the eyesight lost from his use of Izanagi. When Kabuto Yakushi reincarnated Madara, he operated under a similar hypothesis that Sharingan can be evolved into Rinnegan through combination with Hashirama's DNA. To that end he successfully recreated the Rinnegan in Madara's reincarnated body, though these fake eyes didn't have full access to the original's abilities.

Momoshiki also wields the Rinnegan. Unlike most dōjutsu, and unlike other Rinnegan, his pair are on his palms, and are red as opposed to light purple, reminiscent of the Rinne Sharingan. However, after absorbing the chakra of Kinshiki, Momoshiki's Rinnegan became light purple, and he gained a third one on his forehead.

Sasuke Uchiha's left Sharingan became a Rinnegan when Hagoromo's spirit gave half of his chakra to Sasuke. His Rinnegan has six tomoe split between its first two ripples. If overused and weakened enough, Sasuke's Rinnegan will temporarily lose the tomoe and its full strength until fully recharged. The recharging period seems to be a very long one. Sasuke will also lose the ability to even form his Mangekyō Sharingan and access its powers until they have recharged.

As with any dōjutsu, the Rinnegan can be transplanted into others. Madara implanted both of his into Nagato without the boy's knowledge, and Nagato was able to make effective use of the Rinnegan throughout his life due to his Senju lineage. After Nagato's death, the Rinnegan were taken by Tobi, who implanted the left eye into himself and hid the other because he could not handle the power of both eyes at once. Even so, he was able to use one Rinnegan to devastating effects in the Fourth Shinobi World War. Madara later reclaimed both of his Rinnegan after he was revived and ultimately died with them.

Abilities
The Rinnegan grants the wielder a wide range of abilities without any known chakra requirements to keep the eyes active. Certain abilities are only available to the original owner of the Rinnegan, but the possession of even a single transplanted Rinnegan can grant overwhelming power. Rinnegan are able to see chakra, as well as its flow and tenketsu within the body, but cannot see through obstructions such as smoke bombs. With the Rinnegan, the wielder can master any jutsu as well as all five nature transformations with ease. A Rinnegan user is able to create black receivers, into which they can transmit their chakra across long distances, and fully decipher the contents of Hagoromo's stone tablet. The Rinnegan is able to counter the effects of the Infinite Tsukuyomi, and when combined with the chakra of all nine tailed beasts it can completely negate the technique.

Possessing the Rinnegan grants the user a family of abilities collectively known as the Six Paths Techniques: the gravitational powers of the Deva Path; the menagerie of summons available to the Animal Path; the limitless absorptive potential of the Preta Path; the control over others' souls with the Human Path; the different options of mechanisation of the Asura Path; access to the King of Hell through the Naraka Path. These abilities can be distributed to the Six Paths of Pain — six bodies embedded with black receivers, which the user can control remotely. A seventh ability, the Outer Path, is said to allow the user to preside over life and death, and grants the ability to revive the dead, summon and control the Demonic Statue of the Outer Path, and manifest chakra chains to bind others. The Rinnegan also grants the user a shared field of vision with the Six Paths of Pain, the King Hell, and the creatures summoned through the Animal Path, all of which possess copies of the Rinnegan.

Certain Rinnegan abilities have only been demonstrated by single users: Madara can create corporeal shadows in the invisible world of Limbo, which is only visible to the Rinnegan, and summon meteorites; Sasuke's Rinnegan allows him to shift spaces within a certain range of himself and create a dark portal that allows him to enter in other dimensions; Momoshiki's Rinnegan allows him to absorb ninjutsu on contact and subsequently utilise the ninjutsu he has absorbed and use a space-time jutsu that allows him to come and go from his own dimension.

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.
 * The anime depicts the Rinnegan as being multicoloured in its first few appearances. This is corrected after the Rinnegan starts being depicted in colour in the manga. However, whereas the Rinnegan in the manga is a uniform shade of purple, the anime tends to make the centre-most ring a slightly darker shade of purple.
 * After Deidara and Sasori brought Gaara to the Akatsuki hideout, Pain is depicted with tomoe in his Rinnegan once, this is corrected in the tankōbon version.
 * In Naruto: Shippūden episode 203, the Sage of the Six Paths' Rinnegan are shown as red.
 * Sasuke's Rinnegan has been shown many times with less or more than six tomoe:
 * In its manga début it seemed to have nine tomoe, much like the Rinne Sharingan.
 * When visualising Madara's clone, it had no tomoe.
 * On Jin no Sho's back cover, it was depicted with three tomoe.
 * Prior to Sasuke's Rinnegan appearing in colour illustrations by Masashi Kishimoto, the Naruto: Colour Edition depicted it as being red. This is corrected in subsequent chapters.