What is 'Pathron Ka Mela', celebrated in Himachal the day after Diwali?

A centuries-old 'Pathron Ka Mela' is held the day after Diwali in Himachal Pradesh's Dhami. As part of the tradition, two groups of villagers, Halog and Jamog, pelt stones at each other until someone is injured and starts bleeding. The blood is then smeared on the forehead of Goddess Kali, as the injured person is considered an honoured devotee.