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.

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 Gaara and the Fourth Kazekage.

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.

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 assumed 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, many years", while also explaining that the one known as Orochimaru knew the Second Hokage's technique as well. Mū later informs to the Second Mizukage that they're controlled and forced to do some movements, much to the latter and the Raikage's dismay.

As he and the other resurrected Kage approach their targets, he discovers that their targets, Ōnoki and Gaara are retreating due to their undecided plans. He then agrees with the Second Mizukage that taking the lives of shinobi from their own village is unimaginable. Shortly after, he detects that their enemies are approaching, which is followed by Gaara's sand. However, it isn't long until the Fourth Kazekage swiftly counteracts by using his Gold Dust. Upon this event, he later spots Ōnoki about to initiate the Dust Release: Detachment of the Primitive World Technique. He tells him that he is surprised that he was able to live this long, which he then assumes is due to the kekkei tōta. To counteract, he uses the same technique, which created a huge crater in the middle of the battlefield. Ōnoki then states that his predecessor's strength hadn't waned at all.

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.