
Thirumulisai Alvar.
He had the access and resources to learn about various religions because in one of his couplets he says "After my futile efforts to know the supreme principle through Jainism, and Buddhism I am blessed by Shriman Narayana to take refuge at the Lotus feet of Shri Devi and have escaped all problems and misfortunes since then".
There is also evidence in his couplets that show that he asked God to help reveal their ignorance to them. Legend also says that when he displeased the pallava king and was banished, he asked the God from the Temple, Yathotkari, to leave with him. Vishnu is said to have rolled up the snake Sesha like a matress and left with him