The eighth avatar of Vishnu, and the Mahabharata's guiding presence — charioteer, counselor, and, in the Bhagavad Gita, the voice of the epic's central teaching on duty.
महाभारत · Mahabharata
Krishna serves as Arjuna's charioteer and advisor throughout the Mahabharata, refusing to fight directly himself while offering his army to the Kauravas and his personal counsel to the Pandavas. His teaching to Arjuna at Kurukshetra's edge, delivered as the armies stand ready, forms the Bhagavad Gita, already covered in this site's Gyan-Vigyan chapter.
Krishna's own life before Kurukshetra, his childhood in Vraj, his slaying of Kansa, his founding of Dwarka, is told at length in the Bhagavata Purana and reflected through the temples already featured in this site's Tirtha & Devalaya chapter — Dwarka, Banke Bihari, and Govardhan among them.