Could make him lose sleep and kill him.
OT III, also called “The Wall of Fire”. Deals with Incident 2, Xenu, the evil galactic overlord, and the H bombs on Hawaii 76 million years ago. Hubbard said that anyone who was exposed to this level casually would “freewheel” through it, become a chronic insomniac, then get sick and die. “Locating and auditing of body thetans on Incident I (first incident in MEST universe) and Incident II (incident which caused the degradation of these beings into body thetans and clusters as caused by Xenu approximately seventy-five million years ago). Emphasis on this level is ridding the pre-OT of body thetans which are conscious enough to respond to the auditing. Available at Advanced Organizations and higher. Partially replaced by New OT V.” – Jonathon Barbera“This Solo-audited level goes through what is called the “Wall of Fire” that surrounds a previously impenetrable whole track mystery. What prevents a being from being himself? This level answers that question. Once complete, a being is free of the whole track overwhelm that has trapped him. Here he confronts and eradicates the fourth dynamic engram that has plagued this universe for millennia.”The Clear learns about the catastrophic event that placed body thetans on Earth and deprived them of their operating abilities. The Clear is trained to audit the thetans inhabiting his or her own body regarding this incident.
http://listverse.com/2007/07/28/top-8-levels-of-scientology/