In Hinduism, Krishna is the eighth avatar of Vishnu, the Preserver. Described as a blue-skinned young boy playing a flute, he battled many demons and waged war alongside a man called Arjuna. He is a famous deity in the Mahabharata and he is believed to have written the Bhagavad Gita.
"A divine hero of Hindu mythology. He is the eighth avatar of Vishnu, who is said to appear whenever the world is at risk. Name is sometimes translated as "all-attractive." Raised by cow herders. As a boy, he would play his flute, causing women to flock to him. As an adult, he became a great tactician. Shot in the back of the leg by mistake by a hunter named Jara."
—Shin Megami Tensei IV Apocalypse Compendium
Krishna interrupts the war between the forces of God and Lucifer as the representative and main leader of the Divine Powers. The two rebuff the interruption of the war by the gods to instigate a three way war between Monotheism, Polytheism, and Danu's fairies (who wish humanity to not be dependent on gods). He intends to manipulate everyone to achieve his objectives. At the beginning of the game, he is sealed within an ark in Kanda-no-yashiro in Tokyo, but Odin manipulates Nanashi and Asahi (with a little help from Dagda, if Nanashi attempts to negate Odin's manipulations) into freeing him. He immediately sets out to convince Flynn to join them as his "Kalki", his own version of the Godslayer. His ultimate goal is to use Inanna to power the Cosmic Egg and force a rebirth of the universe, with himself or one of his compatriots at the center-thus supplanting YHVH as the Creator and permanently claiming the new universe for Polytheism. He has a messiah complex and has an extremely patronizing view of humans, seeing them as expendable in his goal of universal salvation.
To unlock him for fusion, the player must return to Kanda-no-yashiro after defeating Vishnu-Flynn and Krishna will then lend Nanashi his power to fuse him.