He achieved notoriety in the years following World War II as the author of controversial stories which were printed in science fiction magazines, (primarily Amazing Stories), in which Shaver claimed that he had personal experience of a sinister, ancient civilization that harbored fantastic technology in caverns under the earth. The controversy stemmed from the fact that Shaver and his editor/publisher Ray Palmer claimed Shaver's writings, while presented in the guise of fiction, were fundamentally true. Shaver's stories were promoted by Ray Palmer as "The Shaver Mystery".