Kupalo god of the summer solstice. Kupalo is the mature, the aging Yarilo. Yarilo comes into human world Yav every spring to bring new life, fertility and rich harvest. In the summer he turns into Kupalo. His life on the world gradually moves to its end. He has accomplished his mission in our world and sets off for the Underworld, so he can return again next summer. This is why the Kupalo festival (summer solstice) is actually bidding farewell to the old-aged Yarilo - a preparation for his later ritual burial. http://slavpagan.hit.bg/deities.html Kupalo - Koliada