Indra Ōtsutsuki

was the elder son of Hagoromo Ōtsutsuki and the ancestor of the Uchiha clan.

Background
Indra was the first son of Hagoromo, and inherited his strong genes. From a young age, he demonstrated a great aptitude towards ninshū and anything else he applied his mind to. Due to his prowess, he led a solitary life as he felt no need to depend on others.

When their father was on his deathbed, Asura Ōtsutsuki, Indra's younger brother, was chosen to carry on his dream of establishing peace throughout the world. Indra, believing that he should have been chosen instead as it was his birthright, was manipulated by Black Zetsu into fighting Asura. Both brothers died fighting over the title of the successor of Ninshū, but not before having offspring who would continue this feud for centuries to come. Indra's eventual descendants — the Uchiha clan — would feud with Asura's eventual descendants — the Senju clan. Neither clan knew why or how their hatred of the other came to be.

Personality
Born with his father's talent, Indra understood that his own power was special and different from those around him. He became proud and independent, determined to walk his own path unaided. As he did everything with his own power alone, he believed power and force could achieve anything, even peace. This was an ideology he shared with his paternal grandmother. Though he loved and respected his father greatly, he eventually came to hate both him and his brother due to his father's decision to anoint Asura as his successor. Black Zetsu took advantage of Indra's resentment, who led Indra to challenge his father's decision. Indra's hatred and ideology would have dire consequences for his descendants.

Appearance
Indra had long brown hair cut short on top. Two locks wrapped in bandages framed either side of his face. His eyebrows were cut short — a symbol of his nobility — and his eyes had blue markings around them, which were turned up at the corners. He wore a high-collared, light-coloured kimono held closed by a dark sash. The collar of the kimono was adorned with magatama. He wore a black full-bodied suit underneath. When battling Asura, he wore full-body armour, and his hair had been let out to flow around his attire.

Abilities
From a young age, Indra was recognised as a prodigy, even by his legendary father. Indra inherited his father's "eyes": his powerful chakra, dōjutsu, and spiritual energy. From birth, Indra had a great aptitude for battle. In battle, he also wielded a sword, showing expertise in kenjutsu.

Dōjutsu
Indra possessed a derived form of his grandmother's dōjutsu; the Sharingan. Thus, he could observe the flow of chakra, pay great attention to detail, and accurately predict a person's movements. As a Yin-release user, he could presumably use his Sharingan for genjutsu. In time, he also awakened the Mangekyō Sharingan. With it, he unlocked the ability to use Susanoo. Owing to his talent, his mastery over the technique was such that he could use Complete Body — Susanoo, which dwarfed the surrounding landscape. He would use it to combat Asura's own battle avatar.

Legacy
Though his body was destroyed, Indra's chakra would continue to exist. His chakra reincarnated into various individuals throughout history, and his reincarnations would also inherit his will. Indra's desire for his father's title led to centuries of bloodshed and conflict between his and Asura's descendants.

During the Warring States Period, Madara Uchiha was his reincarnation. With his help, Hashirama Senju, the reincarnation of Asura at the time, created the very first ninja village, Konohagakure, and helped set up the contemporary ninja system. However, due to his ambition, insecurity, and Black Zetsu's machinations, Madara defected, and resumed his conflict with Hashirama. After their final fight at the Valley of the End, Madara stole Hashirama's DNA, which he later implanted into his wounds. A portion of Asura's chakra merged with Indra's chakra within Madara, and eventually, he awakened the Rinnegan, something Hagoromo warned against.

When Madara and Hashirama died, the transmigration cycle resumed. Sasuke Uchiha became the latest inheritor of Indra's chakra and will, with Naruto Uzumaki inheriting Asura's chakra and will. Due to the centuries old conflict that arose from Indra's hatred and Hagoromo's decision to anoint Asura, Hagoromo's spirit decided to grant his power to both Naruto and Sasuke when he was able to appear before them. He hoped that the hatred felt by Sasuke would turn into love, and that his sons' reincarnations would be able to work together.

Ultimately, Naruto managed to accomplish what all of the previous reincarnations had failed to do: end the rift between the two lines of the reincarnated brothers. Naruto achieved this after defeating Sasuke, who finally accepted Naruto's ideals at the end of their fight. This brought about the end of the bitter feud that had lasted for centuries. According to Black Zetsu, the reincarnations of Indra and Asura were almost always in conflict with each other and rarely worked together. Naruto and Sasuke are one of the exceptions, assuming other exceptions have existed throughout the centuries.

Trivia

 * "Indra" literally means "King of Gods" in Sanskrit, a possible reference to his obsession with his father's title.
 * The rivalry of Indra and Asura and their descendants (Uchiha and Senju) is derived from Hindu and Buddhist religions where the Gods, led by Indra, are in constant battle against the Asuras. In the teachings, Asuras were malevolent and the deities were benevolent, but the roles are reversed in the Naruto series.
 * Like his father, he wielded a sword in battle. His choice of main weapon could represent his lust for power, while his brother's choice of a shakujō could symbolise his desire for love and peace.