The image in the sanctum facing west is Swayambhu or self-born. It is almost four to five feet tall and is permanently fitted with a gold plated cover done for the protection of the image. The cover is in two portions, one up to the waist and the other above. Both the parts are joined together so firmly that they are not visible as separate ones. It is said that earlier there was a hole on the pedestal in front of the deity. The water filled here was regarded as a teerth. However, once, a piece of kadali plantain fell in the water. The priest of the temple then tried to remove it by piercing the hole with the help of a sharp instrument. He then heard a cracking sound of the stone and the tool fell from his hand. Subsequently, the teerth also dried up. It is believed by the people that below the sanctum there is a cave and also a golden Vilwa tree. According to them it is for this reason that the place is known as Vilwamala.
According to another legend once, the power of the Lord Vishnu increased enormously. The asuras or demons feared that they might be defeated. Hence for their security one asura disguised himself like a Brahmin and came to the temple. He mixed freely with other Brahmins and participated along with them in the temple feast. One night he killed the cows and other animals and ate their flesh. He threw the bones and horns at one place which became a heap. The priests of the temple were horrified at this incident and hence they began praying to God. One dark night in the month of Kumbha when everyone was fast asleep the asura broke open the sanctum and tried to destroy the idol of the Lord. Lord Vishnu then assumed the form of Narasimha i.e. half-man and half-lion. He fierce fully fought with the asura and tore him to pieces. Hearing the wailings of the demon all the local people and the priests gathered in front of the temple. They all became frightened at the fierce form of the God. Vilwamangalathu Swamiyar, a priest then came forward and began singing hymns of the Lord and addressed him as Vilwadri-natha. Hearing the stotras the Lord calmed down and assumed his benign form. The people were overjoyed and started addressing him as Vilwadrinatha after the name of the sage.
(Last Updated on : 24-08-2012)