Nuo is one of China's oldest rituals: performers in carved wooden masks of gods and demons dance to drive out plague and evil spirits, traditionally at the turn of the year. Over the centuries the ritual grew into nuo opera (傩戏), still performed in villages of Guizhou, Jiangxi, Hunan and Anhui, with its fierce, brightly painted masks. The masks are what most often reach the screen, as a shorthand for the eerie and the ancient. In Blood River, Su Muyu and his twelve zodiac-named assassins wear masks drawn from nuo.
