Here is your short paragraph on Bhatheli/Sori/Suwari/ Parwa:
This festival is prevalent in the old district of Kamrup and Goalpara of Assam and is basically a magical rite associated with fertility-cult. Bodo-Kacharis community call it Bhaitheli.
They plant a tall decorated bamboo is a field, make a small hut close by and offer there eatables, a black pigeon and a black goat for their gods and goddesses and pray to them that they cause no harm to the village and that they leave the people in peace and go downstream.
Kacharis symbolize the departure of the gods by putting the offerings and the pigeon and the goat on a raft and letting it loose in the river. Bhaitheli means going downstream.