Si-Donyi is the major festival celebrated among the Tagin tribe residing in upper subansiri district of Arunachal Pradesh in North-eastern India.
The festival was first conceptualised in the year 1975 by Late Tatar Uli, who was the main pioneer in inception of Si-Donyi uyu.
They believe that when Hilo is chanted, individual family/ or clan sacrifice Mithun(Buffalo)to king of the Evil Spirit.
And they believe that Si(Earth) and Donyi(Sun) are the Goddess and God of the people and so both Si-Donyi and Hillo have huge different with each other.
Controversial is still going on and first group is planning to celebrate the Festival by name of the existing one separately 2024 Si-Donyi onward.
Nibu or the local priest presides over the festival by chanting UI (a form of verbal prayers) to the deities, Si and Donyi in particular.