Snakes dominate the ecology of Kerala. Shrines have been dedicated to them through the length and breadth of the land. The folk lore has been deeply influenced by stories, songs, and rituals relating to snakes. They are integral to the myth of the foundation of Kerala by warrior-saint, Parasurama, incarnation of Vishnu. He 'reclaimed the land from the sea' to form Kerala, and settled Brahmins there. The first set was frightened by the snakes they found everywhere, and fled. Parasurama had to recruit another set. He instituted new customs for them. So he ensured that they too would not desert.
He ordained that, in every household compound, a quarter of the area should be reserved for the snakes. The site should be cool and near a tank. The land there should not be tilled. Trees should be planted there. Buffaloes, dogs, domestic poultry birds, and women should not be allowed in or near them. He thus prevented calamitous snake-human interfaces. He appointed Brahmin (Nambudiri) lineages of Pambummekkavu (Thrissur) and Mannarsala as the special guardians of snake deities. He reinforced traditional snake-worshippers of Kerala, the Pulluvar, to conduct worship even in the households of the Brahmins.
As time passed by, the forests dwindled, the sacred groves dedicated to the snake gods have grown smaller, but they remain. Parasurama, they say, concecrated two temples. One dedicated to Anantha at Vetticode near Kayamkulam and the other, to Vasuki at Mannarasala. The main festival is the Ayilyam. The Ayilyam in the Malayalam month of Kanni (September - October) is celebrated at Vetticode and the other in the month of Thulam (October - November) at Mannarasala.
The Ayilyam puja at Vetticode, which falls in the Malayalam month of 'Kanni', many say, marks the start of the festival season. It is an eight day festival which ends on the Ayilyam day. Thousands of faithfuls gather at this shrine. It is said that Lord Brahma noted the auspisious time and Lord Siva received the dakshina making Vetticode a place where the Hindu Trinity had once made their presence felt.
The festival at Mannarasala, which falls in 'Thulam' is special too. The legend goes back to Parasurama again and then to a generous brahmin lady. This brahmin lady, it is said took care of the snakes that escaped the fire at the Khanvdava forest. The lord of the snakes, pleased with her said that he would be born as her son. She gave birth to a five hooded snake, before he vanished, he said his mother could do the pujas. To this day, the custom continues.
The other famous naga temples are Pambummekkattu Mana, Nagampoozhi Mana, Pambady Nagaraja Temple and a couple of temples in Kottayam district.