Legend of Poornathrayeesa Temple
Legend has it that, the son of Bhavathratha, a famous scholar and an authority in all the four Vedas, Puranas and Ithihasas was living in Dwarakapuri. Though learned, he was arrogant. The Brahmin was overjoyed at his wife's pregnancy and believed himself to be doubly blessed,which added to his arrogance. But his wife gave birth to a still infant though all the religious rituals were performed by Him duly.
The pious Bhavathratha was deeply saddened by this, but his son's grief manifested itself in anger which made him abuse Lord Krishna in front of His palace.
After that incident, the Brahmin's wife gave birth to another 8 more infants and all of them died soon after birth. The Brahmin brought every child in front of the palace and abused Krishna for the death of his baby and took away the baby for the funeral. The Lord did not come out, even once, to face the Brahmin and console him.
Arjuna, who was at Dwaraka at that time, could not remain patient on hearing the abuse of Brahmin towards Sri Krishna. He went to the Brahmin and asked him to stop abusing Sri Krishna. The Brahmin then turned to Arjuna and asked him to protect his next child. Arjuna then revealed his identity to the Brahmin and promised that he will protect the next child.
Arjuna was so overconfident about his prowess that he promised the Brahmin that if he could not protect the Brahmin's next born child, he will commit himself to pyre. During the tenth labour though Arjuna stood on guard, even the mortal remains of the child was not found, though all certified that the birth had taken place. The Brahmin started abusing Arjuna also and asked him to keep his word.
Arjuna then went to the Yama Loka and enquired Lord Yama about the child who was totally unaware of child's death. Arjuna then decided to give up his life when Krishna intervened and took Arjuna to "Vaikuntha", There, they saw all the kids of the Brahmin, playing around Maha Vishnu. Arjuna then prayed to Mahavishnu to stop return the kids to the Brahmin readily returned the kids to Arjuna, along with an idol of Vishnu.
The brahmin was overjoyed to find his children. The family of the present Tanthri of the Temple. Puliyannoor Mana is said to be the descendants of the Brahmin.
Arjuna then requested Lord Ganesha to find a suitable place to install the idol. Ganesha came to a place called the 'Poorna Veda Puram', the present Tripunithura and attracted by the holiness of this ancient Vedic Village, himself occupied the place. It is said that the angry Arjuna kicked Ganesha aside to the southern side of the sanctum Lord Ganesha still occupies the southern part of the sanctum, unlike the common tradition, where Ganesha has a separate shrine at the south-western side of the inner prakara and installed the idol in that holy place, situated amidst mustard fields.
Valia Vilakku It is said Arjuna plucked some mustard seeds and crushed them to get oil for lighting lamp in front of the idol. Devotees consider the evershining "Valia Vilakku" situated in front of the idol, as the oil lamp lit by Arjuna. It is said that the warm oil of this traditional lamp possesses great medicinal value.
Keda Vilakku Inside the Sreekovil, there is a "Keda Vilakku"(lamp which burns forever) which is the first lamp lit by Arjuna during the original Pratishta. It is said that Arjuna gathered gingelly seeds from a nearby place, made oil out of the seeds and lit the lamp. Hence, the present Vazhipaadu of Sree Poornathrayeesa is the 'Olpenna' (offering of gingelly oil) to commemorate that occasion. This is said to be the most important Vazhipaadu in this temple.