A Yao festival celebrating their ancestors, not held every year, sometimes only every 12 years, in some Yao area. Possibly not held by Yao in Yunnan, but only Guangxi.
We do not really have any information on this festival or its locations. For more info, maybe look at http://ks.cn.yahoo.com/question/1406050904684.html or http://www.lbx777.com/ywfj/ssmz/yz/yz04.htm or http://travel.gxcity.com/201006/8206.html