napinnai.

Nila Devi, also spelt as Niladevi and Neela devi is a Hindu goddess and the third consort of the god Vishnu, along with Shridevi (Lakshmi) and Bhudevi (the Goddess of the Earth). She becomes the consort of Vishnu in his avatar as Krishna. She is popular in South India, particular in Tamil culture as a consort of Vishnu. Nila devi's forms include Nagnajiti, Vimathgira, Mathithegi, Rathyambala and Risanika. Nila devi is identified with Nagnajiti, a wife of Krishna or Nappinnai (Pinnai, a favourite Gopi of Krishna in Tamil tradition)

 Goddess Vimathgira was an incarnation taken by Nila devi to slay the evil demon Ratkiraasura. Ratkiraasura was born as Vipulaasura in his previous birth and was killed by Goddess Prathyangira ( Lord Narasimha's divine energy and a form of Goddess Lakshmi). In order to take revenge, Ratkiraasura tried to disturb Lakshmi, but Nila devi came in the form of Vimathgira and destroyed Ratkiraasura. Lakshmi then thanked Nila devi for her help.

Niladevi appears in the Vaikhanasa Agama text. Some texts mention that Vishnu's Iccha shakti takes three forms: Shridevi, Bhudevi and Niladevi, representing the three gunas; The Sita Upanishad mentions that these three forms as those of goddess Sita; Niladevi is associated with tamas. Niladevi besides tamas, is associated with the sun, the moon and fire. She appears as Krishna's gopi in Cherusseri Namboothiri's Krishnagatha.

According to a dhyana mantra of Vishnu, in his Param aspect, he is depicted seated on the serpent Shesha with Lakshmi on his right and Bhudevi and Niladevi on his left. Niladevi may be also depicted standing behind Vishnu with his two co-wives. In a depiction in the British Museum, Vishnu as Vaikuntha-natha ("Lord of Vaikuntha) is seated on Shesha between Lakshmi and Bhudevi, while his foot is supported by Niladev

Nappinnai – Krishna cult is mainly limited to the Tamil-speaking world. The name Nappinnai is found in Divya Prabandha of Alvars and Silappadikaram. Andal (one of the Alvars) wanted to perform devotion to her Krishna like Gopikas did in Dvapara Yuga. She in her Tiruppavai, wakes up Nappinai before waking up Krishna. As per Srivaishnavism, complete surrender to the Lord is performed through his consort and in Sri Krishnaavatharam specifically, it is performed through Nappinai.

Neela devi took incarnation as Nagnajiti, daughter of Kumbagan (brother of Yashoda) and Krishna won her hand after conquering the seven ferocious bulls of her father. Nappinnai's brother is Sudama. Sri Parasara Bhattar describes Krishna, intoxicated by her beauty, as "Neela thunga sthana giri thati suptham".

Velukkudi Swamy, a proponent of Vishishtadvaita Philosophy says that Andal, singing Nachiar Tirumozhi as the daughter of Periyalvar, mentions about Rukmini. But singing as a Gopika in Thiruppavai she mentions only Nappinnai. Alvar mentions the three nachiars (consorts) as Pon mangai (Sri devi), nila mangai (Bhudevi) and pula mangai (Neela Devi) the consort of senses. It is Neela devi who keeps Bhagavan under control by her bhogam. Swami Vedanta Desika says in Daya satakam - "nisAmayatu mAm nIla yat bhOga patalai: druvam". Lord Krishna was a Yadava kshatriya varna by birth, thus he married Rukmini according to that. He was brought up as a Yadava vaishya by varna (gopa), hence he married Nappinnai according to that. Neela suuktam also says - ghruNAhi - ghrutavai - payasvati, etc., mentioning the characteristics of a gopika

Andal, in Her Tiruppavai, imagines Herself to be a Gopika and approaches Lord Krishna. She seeks the help of Nappinnai in placing Her request before the Lord. But who is Nappinnai?