During this time, local residents of Chinese ancestry strictly observe a 10-day vegetarian or vegan diet for the purposes of spiritual cleansing and merit-making. Sacred rituals are performed at various Chinese shrines and temples and aesthetic displays, such as walking barefooted over hot coals and ascending ladders with bladed rungs are performed by entranced devotees known as "Ma Song".
The festival started in 1825 and its paricipants are not allowed to eat meat or have sex at the time of the festival. For obvious reasons participants are asked to use only sterile blades, spears and guns.
Meet Thailand's Phuket Vegetarian Festival.
Sources: 1 | 2 | 3 | 4