R6 implant

Xenu (/ˈziːnuː/), also called Xemu, was, according to Scientology founder L. Ron Hubbard, the dictator of the "Galactic Confederacy" who 75 million years ago brought billions of his people to Earth (then known as "Teegeeack") in DC-8-like spacecraft, stacked them around volcanoes, and killed them with hydrogen bombs. Official Scientology scriptures hold that the thetans (immortal spirits) of these aliens adhere to humans, causing spiritual harm.

These events are known within Scientology as "Incident II", and the traumatic memories associated with them as "The Wall of Fire" or "R6 implant". The narrative of Xenu is part of Scientologist teachings about extraterrestrial civilizations and alien interventions in earthly events, collectively described as "space opera" by Hubbard. Hubbard detailed the story in Operating Thetan level III (OT III) in 1967, warning that the "R6 implant" (past trauma) was "calculated to kill (by pneumonia, etc.) anyone who attempts to solve it".

Within the Church of Scientology, the Xenu story is part of the church's secret "Advanced Technology", considered a sacred and esoteric teaching, which is normally only revealed to members who have completed a lengthy sequence of courses costing large amounts of money. The church avoids mention of Xenu in public statements and has gone to considerable effort to maintain the story's confidentiality, including legal action on the grounds of copyright and trade secrecy. Officials of the Church of Scientology widely deny or try to hide the Xenu story. Despite this, much material on Xenu has leaked to the public via court documents, copies of Hubbard's notes, and the Internet. In commentary on the impact of the Xenu text, academic scholars have discussed and analyzed the writings by Hubbard and their place within Scientology within the contexts of science fiction,UFO religions,Gnosticism and creation myths.

...
Wikipedia