Indra Ōtsutsuki

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

Background
Indra was the first son of Hagoromo, inheriting his father's eyes, his powerful chakra, and spiritual energy. From a young age, he demonstrated great talent towards ninshū and anything he applied his mind to. Because of his prowess, he led a solitary life — finding no need to depend on others. When Hagoromo was on his deathbed, he selected Indra's younger brother, Asura, to carry on his dream of establishing peace throughout the world.

Angry and jealous that his father had not chosen him, Indra, being tempted by Black Zetsu, fought against Asura to claim what he believed should have been his birthright. His descendants, who would become the Uchiha clan, would continue this fight with his younger brother's descendants, the Senju clan.

Personality
Recognising his own talents, Indra became proud and independent, determined to walk his own path unaided. He believed that force and strength were the ultimate key to peace, and though he loved his father greatly, Black Zetsu was able to take advantage of Indra's resentment towards Asura, making Indra challenge his father's decision to let his younger brother carry on his will.

Appearance
Indra had long black hair cut short on top, with two locks wrapped in bandages framing either side of his face. His eyebrows were cut short — a symbol of his nobility and his eyes had markings around them, which were turned up at the corners. He wore a high-collared, light-coloured kimono held closed by a dark sash. Around the collar of the kimono was adorned with magatama under which he wore a black full-bodied suit. He was also depicted in full-body armour. He had allowed his hair to grow out flowing around his attire.

Abilities
From a young age, Indra was recognised as a prodigy even in his legendary father's eyes. Having inherited his father's powerful chakra and spiritual energy, Indra possessed a devolved version of his father's dōjutsu; the Sharingan. He would also awaken its enhanced form: the Mangekyō Sharingan which is presumably the spiral-like pattern which originated at his pupils and covered his irides, which was shown when he debuted.

With it, he became the first wielder of Susanoo, which he could manifest in its stabilised "final" form. Indra also wielded a sword in battle.

Legacy
Hagoromo noted that Indra's chakra remained after his body was destroyed and it was reincarnated into various individuals through history. Madara Uchiha, the previous reincarnation, helped create the first ninja village with Asura's reincarnation, Hashirama Senju. However, he eventually fell to the ideology of Indra, due to various occurrences and continuously sought more power. His growing ambition led to him to covet and eventually steal Hashirama's DNA, inadvertently gaining a portion of Asura's chakra and implanting it in himself. As a result of this, Madara awakened the Rinnegan. After Madara's death, Indra was reincarnated into Sasuke Uchiha.

According to Black Zetsu, the reincarnations of Indra and Asura are almost always in conflict with each other and rarely work 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.
 * 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.
 * Indra's deep hatred toward his brother, a result of his father choosing the latter as the successor of ninshū, may have transcended down throughout his lineage and become part of what is known as the "Curse of Hatred".
 * Like his father, he wielded a sword in battle. His choice of weapon could represent his lust for power, while his brother's choice of a shakujō could symbolise his desire for love and peace.