Mu

Mū (無, Mū) was the Second Tsuchikage (二代目土影, Nidaime Tsuchikage; Literally meaning "Second Earth Shadow") of Iwagakure.
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Background
During his lifetime, Mū taught Ōnoki how to use Dust Release. At some point in time, both he and Ōnoki met with Madara Uchiha, after an alliance had been formed between their respective villages. However, despite their standing, Madara boldly declared that Konohagakure remained the dominant power and as such, they should obey any orders given. This culminated in both parties engaging in battle where Mū and Ōnoki were defeated.[2]
He also had a great enmity with the Second Mizukage and the two men eventually killed each other in what would be their final confrontation.

Personality Edit
Mū was an extremely calm and collected individual, showing no signs of perturbation to his sudden reincarnation. He's also unfailingly polite, taking his time to recount the previous events to the other Kage upon their forced summoning, and referring to the one whom he both killed and in turn was killed by with an honorific title, apparently bearing no ill-will towards him.
Despite the seeming civility displayed towards his fellow Kage, Mū has demonstrated that he first and foremost prioritises the prosperity of his own village regardless of the manner in which this affluence is achieved, even reminding his disciple to take full advantage of any post-war situation to assure the dominance of Iwagakure by quickly seizing control of the resultant spoils.[4] Even seconds before his sealing he attempted to warn Ōnoki to take precaution.[5] This devious and somewhat merciless trait appears to be just one of the many reasons as to why the Second Mizukage despises him to such an extent. This under-handed tactic would later be taught to his student, which would become the reason for Iwa's bad reputation among the Five Great Shinobi Countries.