Interview with Uncle:
First, we will decorate nearby places with tender coconut leaves. Then we will draw kallams with 5 colors and sing Pulluvan Pattu. In all the performances there will be women, usually virgins, who become possessed. This possession is known as thullal. They will get possessed and chant something like "I am happy" or "I am not", or that the rituals have been performed incorrectly. The ritual is done as an offering to snakes. In some places its called Sarpapattam, Nagakallam, or Parunthullal. After the kallam there is one more ritual called Pervazhuthi kudiruthukaa.
When I was with my father, in my early 20's, I went with him to a place to do a kallam. In that place there was no separate idol where daily poojas were performed. There was a forest there at one time but the family had cut down all the trees. Sometime after this, members of the family started getting some bad skin disease which couldn't be cured by any type of medicine or doctors. They went to the astrologist who did the proper calculations and informed them that it was because the snakes were angry and were punishing them. Someone had apparently cut down a snake's house or a place sacred to them. In order to fix this the family would have to organize a 2 day Sarpam thullal. The date was confirmed by my father.
On the fixed date we went to perform. As I mentioned there was no idol, so we arranged one for them, a chitrapeeda sanadha vittivekul (idol of a snake), we also set up a kavu (grove) with the idol. Nobody knew where to keep this new idol because all the forest had been chopped down. The householders selected a place for it. The head of the house placed flowers where he wanted the idol, and we consecrated the idol in that spot. Near the idol we placed a Palkindi (Kindi means vessel). In this palkindi milk, rice and flour are mixed as an offering to invite the snakes to the ritual. When the children became possessed the others were watching from the verandah (outside every Kerala home there is a verandah)pulling apart a pile of white flowers and areca nut, to be used later in the ritual. While doing this a snake came out of the flower, which scared the children, but it quickly scurried away. Nobody knew where the snake could have come from. At any rate, the ritual was performed and the family was cured from the disease.