The Wall of Fire.
Evil Xenu, the ruler of the Galactic Confederacy, transported billions of aliens to Earth and killed them in volcanoes using hydrogen bombs. After this, their immortal souls, thetans, ascended into the atmosphere where they were captured and placed in 3D cinemas where they were brainwashed using films (the so-called R6 implant). Then the thetans were released and have since clung to humans as spiritual parasites ("body thetans") and caused various problems. The goal of the higher levels is to free oneself from these body thetans with the help of auditing (from Wikipedia).
The piece above is not from a science fiction book. The text is from a "religious philosophy" book by Ron Hubbard, Scientology: A History of Man. This text is the most notable of the Church of Scientology's secret teachings and is said to have taken place 75 million years ago.
Ron Hubbart was the founder of The Church of Scientology; before he founded The Church of Scientology, he was a writer of science fiction, western, fantasy, etc.
Around 1950 he started The Church of Scientology based on an earlier dianetic theory.
In dianetic, they use something they call an auditing aid. An electropsychometer, E-meter, is connected to a person's body (by holding two cans attached to the so-called E- meter). By following a script, they have a hearing with ”patients." They keep asking questions repeatedly until the E- meter doesn't show any response to the questions.
A sort of brainwash.
These audits are pretty expensive, so most people have to borrow money to afford the sessions.
The Church of Scientology has connections to some lending institutions and helps people with loans.
To reach a higher level in The Church of Scientology, you also have to do some "education." These are also expensive courses, and people have to keep on borrowing money to reach these higher levels.
Some people have depths of $20000 and more to pay off.
If you don't afford the courses, you have to work for free at the Church. Often this work is to hunt new members. Their workdays are long and hard.
In October 2009, the Church of Scientology in France was convicted of organized fraud. According to the ruling, the church has systematically cheated its members of their savings.
In Sweden, the Church of Scientology has been embroiled in a controversy that began when Swedish Scientology critic Zenon Panoussis submitted a copy of the NOT documents ("New Era Dianetics for Operating Thetans") to the Swedish Parliament. The documents, which were copyrighted by the Scientology movement, thus became public. The Church of Scientology attempted to keep the public from reading the documents by having members sit and read them or simply sitting on the stack of paper during office hours. Between 1997 and 2000, the Church of Scientology attempted several times to have the documents removed from the Riksdag's office. Several attempts to classify them were unsuccessful. The documents were stolen twice.
The Church of Scientology denies any involvement, but critics suspect them. Panoussis was found guilty of copyright infringement and ordered to pay damages and legal fees in 1998. After three years of repeated attempts by the Church of Scientology to keep the NOT documents secret, the Riksdag passed a law supporting the documents secret in 2000. Several lawyers objected, claiming that copyright had taken precedence over Sweden's constitution. The documents, however, are still freely available online at Wikileaks under the title "Scientology cult New Era Dianetics for Operating Thetans."
As many of those "free" Churches, they have celebrities as members to reach people. In The Church of Scientology are names like Tom Cruise and Katie Holmes well known. John Travolta and Elisabeth Moss are also names and members of The Church of Scientology. Probably well paid for their membership by the Church (my reflection, not confirmed).
And like many cults, such as The Church of Scientology, people criticizing the Church are not allowed to meet the believer. In the Church, a criticizer of the Church is called a suppressive person. That makes the believer cut off the rest of the world. I am probably now a suppressive person, I guess.
Many defectors have talked about the mental difficulty of leaving the Church. The brainwashing is so deep, and it takes years to normalize their personality.
The doctrine is dictatorial, and you are not allowed to criticize anything.
According to Dr. Poulter of Wikimedia UK, the Church of Scientology was the first organization to be barred from editing Wikipedia in 2009, after creating several accounts that all edited in the same pattern of deleting critical material and inserting Scientology propaganda.
That is the most dangerous with all cults, not allowing criticism, making you a scared person and constantly watching your tongue, afraid of what can happen if you say something improperly that makes your position wrong.
It is like any dictatorial government—management, controlling people's minds by fear.