Yata Mirror

The second of Itachi Uchiha's weapons which he added to his Susanoo, the Yata Mirror provides one of the highest defenses ever seen in the series, increasing the Susanoo's already formidable defenses to a higher level. The Yata Mirror is a one of the three legendary treasures, and being endowed with all nature transformations, it can change its own characteristics depending on the characteristics of the attack it receives. As such, it is able to block all attacks. Zetsu claimed that this, combined with the Sword of Totsuka, essentially made Itachi invincible.