Agni is a kind, welcoming individual, who does his best to make people feel welcome, useful and needed, as shown when he is able to use the Phantomhive servants to accomplish tasks, while Sebastian Michaelis usually dismisses them as idiots. His ability to find the strengths of people and use them has resulted in Sebastian praising him as a capable person. Additionally, Agni is exceptionally humble, frequently stating that he is not nearly as good of a butler as Sebastian and dismissing praise as if he is unworthy of it.
He admires and adores Prince Soma, who he believes is a god, and will do anything to make him happy. Even when appearing to betray Soma, he did so only to protect and aid Soma, and is deeply grieved by his own actions. He does his best to remedy any wrong he commits, even at the insistence of others that he forget it.
Agni is an Indian man with dark skin, dark blue-grey eyes, and mostly short, white hair with two braids that are adorned with beads. He keeps his head wrapped in a plain turban and wears a green sherwani with a yellow and white sash over plain churidars. For accessories, he wears silver hoop earrings and a decorative bindi. He also keeps his right hand and forearm wrapped in bandages, which he only unwraps when calling on the power of his faith in God to accomplish difficult tasks. In the anime, when he calls on this power, his hand glows light blue. His name 'Agni' means 'Fire' in Hindi.
In the past, Agni and his family were Brahmans and were part of the highestcaste that was able to serve God. However, as a boy, he watched his father swim in material goods and human indulgences, which caused Agni to have no faith in God. He also indulged in sins and luxuries available to him, due to his social class. He states that this hurt a lot of people, and eventually, he was called to pay for his sins.
He was to be executed for his sins, and at his execution, he felt that he had no lingering affection for the world and no faith for God. However, Prince Soma attended his execution, because he had heard that Agni was very strong and he wanted him to become his sparring partner. When his attendants told him he could not do that with a criminal about to be executed, Soma cut his hair and said that Agni would be reborn with a new name and a new life. For this reason, it is understood that Agni is not his birth name. Agni accepted this offer because he felt that God existed in Soma.