Stone Tablet

The is a monument which was created by Hagoromo Ōtsutsuki in order to discourage his son's descendants from attempting to recreate the Rinnegan. The tablet can only be deciphered fully by the Rinnegan, while the Sharingan and Mangekyō Sharingan are able to partially decipher it.

History
Some time after Hagoromo's death, certain details on the tablet were forged by Black Zetsu as part of its plan to revive Kaguya Ōtsutsuki. The tablet eventually fell into the possession of the Uchiha clan, where it was secretly passed down for generations. After the formation of Konohagakure, the tablet was kept in the underground bunker of the Naka Shrine.

Contents

 * The secrets of the Mangekyō Sharingan, such as instructions on how to obtain it, and its ability to control the tailed beasts.
 * The story of the Sage of Six Paths, Kaguya and the God Tree.
 * The secrets of Madara Uchiha's body.
 * Warnings regarding Kaguya's Infinite Tsukuyomi.
 * The Uchiha would be saved by the Infinite Tsukuyomi (written by Black Zetsu).
 * The secrets of the Uchiha clan.

More specifically, the following sentences were quoted:

Trivia

 * Despite having neither the Rinnegan, nor the Sharingan, Black Zetsu was able to read and rewrite the text on the tablet.
 * Kabuto Yakushi and Orochimaru, while unable to read the tablet, managed to come up with a hypothesis of the secrets based on many years of research.
 * Obito (as Madara) states that the creation of the moon using the Chibaku Tensei was written on the tablet; however, Black Zetsu later reveals that the Six Paths — Chibaku Tensei was the real cause. It is unknown whether Hagoromo Ōtsutsuki really wrote that version or Black Zetsu merely rewrote that part. In a similar matter Madara states that Hagoromo Ōtsutsuki acted alone defeating the Ten-Tails without mentioning Hamura Ōtsutsuki.
 * The tablet appears in Boruto: Naruto the Movie. Rather than underground, the tablet rests within the forest Sasuke trained Boruto. How the tablet was moved and why it remains after uncovering its deceptions are unknown.