Mangekyo Sharingan is the highest form of the Sharingan, awakened only in a few members of the Uchiha clan who have experienced a traumatic shock, usually associated with the death of their dearest person. The tomoe pattern in the eye transforms into a unique design for each wielder, resembling the blades of a pinwheel. These eyes are called "heavenly eyes that see the truth of all things without hindrance".
In addition to preserving and enhancing all the basic abilities of the Sharingan, the Mangekyo Sharingan grants its owner powerful unique dōjutsu, which usually differ for the left and right eye. For example, Itachi Uchiha possessed Amaterasu and Tsukuyomi, Sasuke Uchiha — Amaterasu and Kagutsuchi, which allows controlling the shape of the black flames, Obito Uchiha and Kakashi Hatake — the space-time Kamui, and Shisui Uchiha — Kotoamatsukami, a perfect genjutsu of suggestion. One who masters the powers of the Mangekyo in both eyes gains access to Susanoo — a giant avatar of chakra. Some wielders, like Madara and Sasuke, possess a "straight tomoe" that grants increased variability of movements in battle.
Each use of Mangekyo techniques causes a colossal strain: a huge amount of chakra is consumed, the body is pierced by excruciating pain, and vision irreversibly deteriorates, and excessive use leads to complete blindness. Only a transplant of the eyes of a blood relative, ideally a sibling, can restore the lost light, forming the Eternal Mangekyo Sharingan. The Uchiha can also program the activation of Mangekyo techniques under certain conditions, and this program remains active even after the creator's death.
A transplanted Mangekyo Sharingan can be used by non-Uchiha, and they are able to freely activate and deactivate it, although the chakra cost for them is noticeably higher than for a true wielder. Moreover, the Mangekyo allows for a deeper deciphering of the Uchiha clan's stone tablet, revealing knowledge inaccessible to a regular Sharingan.
