Isaignaniyar

The Tamil Periya Puranam by Sekkizhar (12th century), which is the hagiography of the 63 Nayanars and the primary source about their life, dedicates just an hymn to her, naming her son and husband.

"As the divinely opulent wife of Sataiyanaar (Sadaiya Nayanar) and as a devotee of the lord who shattered the triple hostile citadels (Shiva as Tripurantaka), the poet realizes the inadequacy of the poetic medium to extol her glory.

The couple gave away Sundarar to Narasinga Muniyaraiyar, the chieftain of Thirumunaipadi and a Nayanar saint, for adoption.

An inscription on the west wall of the second prakaram of the Thyagaraja Temple (dedicated to Shiva), Thiruvarur mentions Isaignaniyar.

[8][9] Sundarar refers to Isaignaniyar in the Tiruthonda Thogai, a hymn to Nayanar saints,[10] which is the first compilation of the list.

[4] Isaignaniyar is worshipped in the Tamil month of Chithirai, when the moon crossed into the Chitrai nakshatra (lunar mansion).

Sundarar's mother Isaignaniyar and another notable Nayanar Sambandar’s "foster-mother" Mangayarkkarasiyar were included in the list due to their maternal links.

Family of Sundarar (l->r): Sadaya Nayanar (father), Isaignaniyar (mother), Paravai Nachiyar (wife), Sundarar, Sangili Nachiyar (wife), Narasinga Muniyaraiyar (foster-father).
The images of the Nayanars are found in many Shiva temples in Tamil Nadu.