The most important San ritual is the communal trance dance or great dance. The participants of the dance move in a circle clapping, singing and dancing rhythmically until they enter trance.Dances are often spontaneous, and can be initiated for play by children. Adults join after nightfall and the dance becomes more intense. Only the most experienced dancers enter trance and are called “owners of energy”. Dancing is painful and entering into trance is frightening to some people. The trance dancers and the spirit world are frequently depicted in San rock art. At the healing dances, the ritual specialists use supernatural potency to send their spirits on journeys to the otherworld where they plead with their god for the souls of the sick. Supernatural potency is called n|om by the Kalahari Ju|’hoansi, and !gi by the |Xam of the Karoo and has been described as being like an electrical current. The invisible energy floats through the air and dancers harness it through a spot on the back of the neck, called the n/ao spot. The energy travels down the spine to the stomach, where it is said to “boil”, before moving back up to the head, where it explodes, catapulting the dancer into the spirit world. Once in the spirit world, dancers must perform various tasks for the benefit of their community. These may include healing the sick, controlling the weather, visiting far-away places and controlling the movement of game.