Xenu

Scientology teaches that Xenu (pronounced (ZEE-noo)) was the dictator of a galactic confederacy of 76 planets, who was captured and imprisoned on Earth 75 million years ago after bringing billions of his people to Earth, placing them around volcanoes and killing them by using hydrogen bombs. Scientologists believe he is still being kept there these days. Xenu is very important to the beliefs of Scientology because the story of Xenu explains the believed origin of what are known as body thetans from humans. Body thetans are believed to be the essence of Xenu's people that gather around humans and cause them spiritual harm. It is the purpose of auditing within Scientology to remove these thetans from the Scientologist.
The existence of Xenu has been reported by L. Ron Hubbard's writings and by Scientology spokesman Tommy Davis in an interview ABC affiliate KESQ-TV.