According to regional traditions, Niladevi took the incarnation of Nagnajiti, a wife of Krishna. In Sri Vaishnavism, Nagnajiti is also called Nappinnai (Pinnai, a favourite gopi of Krishna in Tamil tradition).[10][5]
According to a dhyana mantra of Vishnu, in his Param aspect, he is depicted seated on the serpent Shesha with Sridevi on his right and Bhudevi and Niladevi on his left.[12] Niladevi may be also depicted standing behind Vishnu with his two co-wives.[11] In a depiction in the British Museum, Vishnu as Vaikuntha-Natha ("Lord of Vaikuntha") is seated on Shesha between Sridevi and Bhudevi, while his foot is supported by Niladevi.[11]
Niladevi's aspect of Nappinnai is mainly limited to Tamilakam. The name Nappinnai is found in the Divya Prabandham of the Alvars and Silappadikaram.[14] According to these texts, Andal (one of the Alvars) wanted to offer her devotion to her patron deity Krishna just as the Brajgopis did in Dvapara Yuga. In her Tiruppavai, Andal wakes up Nappinai before waking up Krishna. As per Sri Vaishnavism, complete surrender to God is performed through his consort, and in the case of Krishna specifically, it is performed through Nappinai.[14]
Niladevi took the avatar of Nappinnai, the daughter of Kumbagan (the brother of Yashoda). Krishna won Nappinnai's hand after conquering the seven ferocious bulls of her father. Nappinnai's brother is Sudama. Parasara Bhattar describes Krishna, intoxicated by her beauty, with the epithet "Neela thunga sthana giri thati suptham" (lit. "He who rests on the breasts of Nappinnai").[15]
S. M. Srinivasa Chari states that Andal, singing Nachiyar Tirumoli as a gopika in Thiruppavai, she mentioned Nappinnai. This stands for the identification of Nappinnai as Radha.[16][17] Alvar mentions the three nachiyars (consorts) as Ponmangai (Sridevi), Nilamangai (Bhudevi) and Pulamangai (Niladevi). Niladevi is mentioned to be the goddess of senses. It is Niladevi who keeps mind stable by offering him her bliss.[18]