https://hatch.kookscience.com/w/images/thumb/4/4c/Robert_Gibson_Jones_-A_Scene_in_the_Caves-(AS_v21_n6).jpg/1200px-Robert_Gibson_Jones-A_Scene_in_the_Caves-_(AS_v21_n6).jpg
"The Shaver Mystery had its origins at the height of the Second World War. It was a relatively normal day in 1943 when Palmer was opening the daily delivery of mail that regularly poured into the offices of Amazing Stories, and came across one particular missive penned by a certain Richard Shaver. And weird barely begins to describe it. Shaver wrote that he, personally, had uncovered a sensational and terrifying secret: in our distant past a race of ancient, highly-evolved entities lived right under our very feet. Massive caverns, huge caves, and near-endless tunnels, were the dark, damp places they called home."
https://mysteriousuniverse.org/2012/09/the-strange-saga-of-richard-shaver/
Inner Earth Conspiracy Theories #2
Richard Shaver : The Shaver Mysteries