Mū

was the of Iwagakure.

Background
During his life Mū was the teacher of Ōnoki, whom he taught how to use dust release. He later fought the Second Mizukage in battle. He was able to kill the Mizukage, but the Mizukage killed Mū too before he died.

Appearance
It appears that the entirety of Mū's body is covered by intricately wrapped bandages, with only his eyes and nose visible, giving him an overall mummy-like appearance. These features are accentuated by a dark colored headband with no distinguishing markings and black shorts. Due to the effects of the Summoning: Impure World Resurrection technique, he has black sclera and white irides.

Abilities
Mū is able to become perfectly camouflaged with the surrounding environment. His camouflage is so good in fact that he has become renowned as the "Invisible Man", for it is impossible to detect him by normal means. Mū considers the ability to sense his presence worthy of praise. He himself is also a sensor type shinobi displaying the ability to sense chakra over a distance of several kilometers. He also appears to be able to suppress his own chakra to the point that it is undetectable.

He also appears to be both extremely knowledgeable and analytical, being able to discern the exact method used to locate his position almost immediately after detection, seemingly without any prior information concerning the technique in question.

Mū is a user of the Kekkei Tōta Dust Release, which allows him to use fire, earth, and wind-style jutsu. The dust release makes him so powerful that the Shinobi Alliance feared him greatly, and Ōnoki only trusts himself, also a dust-user, to fight him.

Shinobi World War Arc
Mū, as a former Kage, is resurrected alongside various other notable shinobi by Kabuto Yakushi, in preparation for the Fourth Great Shinobi War. When the Kage are mobilized, Mū is sent in the direction of the Fourth Division. As he approaches their location invisibly he is detected by Gaara's Sand Sensing technique, something which he commended his opponents for achieving.

Upon being noticed, Mū was forced to summon the Third Raikage, the Second Mizukage, and the Fourth Kazekage. Recognizing the means of their revival as the Impure World Resurrection, Mū searched for the Second Hokage, the technique's inventor and thus the assumed user. The Fourth Kazekage then explained that the two had been dead for "many, many years", while also explaining that the one known as Orochimaru knew the Second Hokage's technique as well. While conversing with the other Kage, Mū noted that the summoning technique limited their actions.

Trivia

 * can mean nothingness or non-existence; possibly alluding to his ability to become invisible.
 * His appearance and the technique he uses may be referring to the main character of "The Invisible Man" novel of H.G. Wells.