Shinbyeong (spirit Sickness)
The central feature of a shaman's initiation is her affliction with an illness known as a shinbyeong. This is also called the "spirit sickness" or "self-loss" and characterized by a loss of appetite, insomnia, visual and auditory hallucinations. A ritual called a naerim-gut cures this illness, which also serves to induct the new shaman.
Read more about this topic: Korean Shamanism