A (First Raikage)

was the who founded Kumogakure in the Land of Lightning.

Background
At the first meeting of the five Kage, he was accompanied by the future Second Raikage. He sat alongside the other Kage and told Hashirama that bowing to other Kage was not a sign of a lasting leader. After asking the First Kazekage to give voice to his alternative request, since Sunagakure already had a tailed beast, he expressed outrage when the Kazekage made a demand of receiving 30% of whatever they would pay for a tailed beast from Konoha. As infighting broke out and Hashirama Senju made his plea to them to preserve the future of their children and unite, he looked on intently.

During his leadership, he gave land in the Valley of Clouds and Lightning to the Yotsuki Clan in return for their loyalty. His reign was short lived, as his successor was Raikage during the First Shinobi World War.

Personality
While not much was seen of his personality, A did seemingly have a verbal tic, ending his sentences with. He also seemed to have a habit of folding his arms. He was a prideful man and held the idea that shinobi shouldn't lower their heads so easily. A had a strong will to protect Kumogakure, something he passed down to his successor.

Appearance
A was a dark-skinned man, with prominent creases under his eyes and a mop of shaggy black hair, which partially obscured his forehead protector. In terms of attire, he wore a high-collared dark kimono-shirt, dark pants bound by a sash and a light-coloured scarf around his neck. He also wore small stud-earrings. In the anime, his attire consists of a cream-coloured coat with a high collar, a white forehead protector, zōri and a purple scarf around his neck.

Abilities
As the First Raikage and the founder of Kumo, A was undoubtedly a powerful shinobi.

Kaguya Ōtsutsuki Strikes
Subsequent to Kaguya Ōtsutsuki being sealed by Naruto Uzumaki and Sasuke Uchiha, he and the other deceased Kage were summoned from the Pure Land by Hagoromo Ōtsutsuki to aid him and the Hokage in summoning Team 7, the tailed beasts and Madara Uchiha from Kaguya's dimension. He later commented on the state of things before his and the other Kage's souls were released to the Pure Land once more.

Trivia

 * In terms of appearance, A bears a stark resemblance to music icon Jimi Hendrix.