During 1943, Shaver wrote a letter to Amazing Stories magazine. He claimed to have discovered an ancient language he called "Mantong," a sort of Proto-World language which was the source of all Earthly language. In Mantong, each sound had a hidden meaning, and by applying this formula to any word in any language, one could decode a secret meaning to any word, name or phrase. Editor Ray Palmer applied the Mantong formula to several words, and said he realized Shaver was on to something.
According to Palmer (in his autobiography, The Secret World), Palmer wrote Shaver back, asking how he had learned of Mantong. Shaver responded with an approximately 10,000 word document entitled "A Warning to Future Man." Shaver wrote of extremely advanced pre-historic races who had built cavern cities inside Earth before abandoning Earth for another planet due to damaging radiation from the Sun. Those ancients also abandoned some of their own offspring here, a minority of whom remained noble and human "Teros", while most degenerated over time into a population of mentally impaired sadists known as Deros—short for "detrimental robots." Shaver's "robots" were not mechanical constructs, but were robot-like due to their savage behavior.
These Deros still lived in the cave cities, according to Shaver, kidnapping surface-dwelling people by the thousands for meat or torture. With sophisticated "ray" machinery that the great ancient races had left behind, they spied on people and projected tormenting thoughts and voices into our minds (reminiscent of schizophrenia's "influencing machines" such as the Air loom). Deros could be blamed for nearly all misfortunes, from minor "accidental" injuries or illnesses to airplane crashes and catastrophic natural disasters. Women especially were singled out for brutal treatment, including rape, and Dash notes that "Sado-masochism was one of the prominent themes of Shaver's writings." Though generally confined to their caves, Shaver claimed that the Deros sometimes traveled by spaceships or rockets, and had dealings with equally evil extraterrestrial beings. Shaver claimed first-hand knowledge of the Deros and their caves, insisting he had been their prisoner for several years.
Palmer edited and rewrote the manuscript, increasing the total word count to a novella length 31,000. Palmer insisted that he did not alter the main elements of Shaver's story, but that he only added an exciting plot so the story would not read "like a dull recitation." Retitled "I Remember Lemuria!"; it was published in the March 1945 issue of Amazing. The issue sold out, and generated quite a response: between 1945 and 1949, many letters arrived attesting to the truth of Shaver's claims (tens of thousands of letters, according to Palmer). The correspondents claimed that they, too, had heard strange voices or encountered denizens of the Hollow Earth. One of the letters to Amazing was from a woman who claimed to have gone into a deep subbasement of a Paris, France building via a secret elevator. After months of rape and other torture, the woman was freed by a benevolent Teros. Another letter claiming involvement with Deros came from Fred Crisman, later to gain notoriety for his role in the Maury Island Incident and the John F. Kennedy Assassination. "Shaver Mystery Club" societies were created in several cities. The controversy gained some notice in the mainstream press at the time, including a mention in a 1951 issue of Life magazine.