The most controversial portion of Scientology's space opera is the myth of Xenu, known as "Incident 2", in which Hubbard described a group of 76 planets, orbiting stars visible from Earth, organized in a Galactic Confederacy c. 75 million years ago, ruled by the dictator Xenu.
Hubbard discussed the history of human civilizations on Earth, and the lives of ancient sea monsters and fish people, as well.