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 pants. Due to the effects of the Summoning: Impure World Resurrection technique, he has black sclera and white irides.

When he was still alive, he donned what appeared to be a standard Iwagakure's flak jacket, with the village distinctive single sleeve on his left arm, and had two large swords strapped to his back.

Personality
Mū is an extremely calm and collected person, showing no signs of perturbation to his sudden resurrection. He's also unfailingly polite, taking his time to explain the last events to the other Kage he was forced to summon, and referring to the one who he both killed and was killed by with an honorific title, seemingly holding no grudges against him.

Abilities
Having been the Kage of his village, Mū is considered an extremely powerful shinobi. He 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.

He is also a skilled sensor type shinobi displaying the ability to sense chakra over a distance of several kilometers, as well as to discern the similarity between the chakra belonging to Gaara and the Fourth Kazekage.

In the past, he carried around a large pair of swords, and was probably proficient in using them.

Invisibility
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, for it is impossible to detect him by normal means. He's even able to suppress his own chakra to the point that it is undetectable. Mū considers the ability to sense his presence worthy of praise.

Nature Transformation
Mū is one of the few people capable of using a kekkei tōta, an advanced and extremely powerful form of kekkei genkai: he possesses the Dust Release, which allows him to combine the fire, the earth and the wind element to reduce his opponents to nothing more than dust, destroying them at a molecular level.

The Dust Release makes him so powerful that the Allied Shinobi Forces fears him greatly, and Ōnoki only trusts himself, Mū's former apprentice and also a Dust-user, to fight him, an assertion which Tsunade agrees with.

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, but informs his comrades that he could only pick up the presence of someone whose chakra signature was comparable to the Fourth Kazekage, and that that person is backed by a large army. The Fourth Kazekage then explained that the Second Hokage had been dead for "many, many years", while also explaining that the one known as Orochimaru knew the Second Hokage's technique as well.

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.