The Ashi people of Yi people advocate fire, and they have been attached to it all their lives, from the naming ceremony of the fire pit at birth to various sacrificial activities that are inseparable from fire. They believe that fire brings light and warmth to people, cooked food and drives away fierce beasts, so they regard fire as a god. Legend has it that there was no fire in the ancient Ashi tribe, and the ancestors of Ashi lived a life without light. They not only ate raw meat, but were often attacked by wild animals.

After a flood, an ancestor named Mudeng sat on a rotten piece of wood and used a wooden stick to make holes and grind the ground. Gradually, a spark finally appeared on the third day of the second lunar month, and he became angry. Since then, the wild era of eating animals and blood has ended, the crops on the five-color soil are ripe, and the fire has brought light and warmth to people. Ashi people regard the legendary inventor "Mudenseru" as a "Vulcan" sacrifice, which has been handed down from generation to generation.

Bimo is a transliteration of Yi language. Bi means "chanting" and Mo means "learned elder". It is a kind of sacrificial teacher who praises, prays and sacrifices for others. Bimo is well-connected and knowledgeable, and his main functions are as a priest, practicing medicine, divination and other activities; Its cultural function is to organize, standardize and teach Yi language, and to write and copy ancient books including religion, philosophy, ethics, history, astronomy, medicine, pesticides, crafts, customs and characters. Bimo plays an important role in the life of Yi people, such as fertility, weddings, funerals, diseases, festivals, hunting and sowing. Bimo is in charge of theocracy, culture, ghosts and gods, and guides personnel. In the eyes of Yi people, Bimo is an intellectual of the whole Yi society and a defender and disseminator of Yi culture.