Mū

was the of Iwagakure.

Background
During his life Mū was the teacher of Ōnoki, whom he taught how to use Dust Release. He also had a great enmity with the Second Mizukage. The two men eventually killed each other in battle.

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-coloured headband with no distinguishing markings and dark 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 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.

Despite his civility towards his fellow Kage, Mū has shown that he still puts the well-being of his own village above all else and even reminded his pupil to quickly win the spoils of war as they did in the past to make Iwagakure stronger. This underhanded mannerism seems to be one of the reasons the Second Mizukage detests him.

Abilities
Having been the Kage of his village, Mū is 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. While alive he carried a pair of what resembles swords wrapped up in bandages.

He is also a skilled sensor type shinobi displaying the ability to sense chakra over a distance of several kilometres, as well as to discern the similarity between the chakra belonging to close relatives such as Gaara and his father. Furthermore, when these detection capabilities are employed in conjunction with his quick reflexes, he can avoid techniques that even other Kage find difficult to evade, as demonstrated when only he instinctively managed to elude the clutches of Gaara's hands made from sand.

Invisibility
Mū is capable of becoming perfectly camouflaged with the surrounding environment. His camouflage is so good that he has become renowned as the, a title which he gained for seemingly having no form, and no chakra, while the technique was active. It is impossible to detect him by normal means. Mū considers anyone with 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. Compared with fellow dust-user, Ōnoki, his power seems to be of equal standards, as when the two initiated Dust Release: Detachment of the Primitive World Technique, the disastrous outcome was chaotic, implying their power on utilising Dust Release is equal. This may be due to the fact that Mū's power hadn't waned, stated by Ōnoki.

The Dust Release makes him so powerful that the Allied Shinobi Forces fear him greatly, and Ōnoki only trusts himself to fight him, an assertion which Tsunade agrees with. Mū himself states that numbers alone do not matter against his Dust Release when facing a large amount of the alliance's soldiers.

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 mobilised, 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. Recognising the means of their revival as the Impure World Resurrection, Mū searched for the Second Hokage, the technique's inventor and thus the presumed user, but informs his comrades that he could only pick up the presence of someone whose chakra signature was similar to the Fourth Kazekage's, and that that person is backed by a large army. The Fourth Kazekage then explained that the Second Hokage had been dead for many years, while also declaring that the one known as Orochimaru knew the deceased Hokage's technique as well. Mū later notifies the Second Mizukage that they're being controlled and thus, some of their movements are restricted, much to the latter and the Raikage's dismay.

Pursuing the division throughout the entirety of the night alongside the others, he discloses that their intended targets have been slowly retreating due to their indecision but that the opposition's movements have now altered, concluding their pursuit. When the Second Mizukage laments upon the prospect of confronting shinobi from his own respective village and curses the one responsible for resurrecting them, even Mū is in agreement. Shortly after, he detects the approach of two persons, who are preceded by Gaara's quicksand that descends upon the four in a colossal tidal wave. However, it isn't long until the Fourth Kazekage swiftly counteracts this through his Gold Dust. Upon this event, Gaara appears suspended above them and summons hands of sand to ensnare the Kage, with only Mū being able to escape captivity while sensing Ōnoki's presence, who appears to have lived a long life thanks in part to his master's teachings. Utilising the same technique to counteract that of his former disciple's, the attacks result in the formation of a huge crater in the middle of the battlefield, leading Ōnoki to assert that his predecessor's strength hadn't waned at all. His suspicions that a shinobi alliance had been formed are affirmed after he states he was wondering why so many chakra types from different villages were accumulated in one place. He reminds Ōnoki that he had to take full advantage of the post-war situation to turn the tides in favour of Iwagakure as an individual nation, something which caused both the Second Mizukage and Third Raikage to lash out at him about. Ōnoki surprises him when tells him that he would do no such thing. When the battle resumes he is chased down by Ōnoki.

Trivia

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