In Hindu mythology, Nandi is a bull that is riden by the god Shiva. He is said to have been born from the right side of Vishnu. He also acts as the gatekeeper of Shiva and Parvati's abode. There are numerous temples dedicated solely to Nandi and stone idols of Nandi are usually present at temples venerating Shiva and Parvati. He is also a gatekeeper of Shiva's abode and one of his watchmen, along with Mahakala.
"Origin: India. A white bull Shiva rides. Its name means 'happy.' His duty is to play music for Shiva Nataraja to dance to. He is the guardian of four-legged beasts and symbolizes fecundity and fertility. A statue of Nandi is commonly placed in front of temples that worship Shiva."
"A sacred cow that serves as the mount of the god Shiva in Hindu tradition. Its name means "fortunate one," and it symbolizes fertility and the harvest. Its body is the color of milk and it carries Shiva and his wife Parvati on its back. Shiva is also known as the god of dance, and when he dances, Nandi plays the music. Nandi is enshrined alongside Shiva in many temples in India. Its statue is always set facing Shiva's so that it is ready to serve its master at a moment's notice."
—Shin Megami Tensei IMAGINE Compendium
Nandi can be contracted within the silver level of Nakano Stone Site. It also appears alongside Shiva when he acts as a boss and alongside Matador on his floor within the Denshi Kairo instance.
Devil Summoner 2: Raidou Kuzunoha vs. King AbaddonEdit
"A sacred male cow from Hindu lore. Said to be Shiva`s mount, Nandi is the protector of all beasts. It is Nandi`s responsibility to play music for Shiva to perform the dance of destruction and recreation."
—Devil Summoner: Raidou Kuzunoha vs. King Abaddon Devil Chart