The text contains information on cults that worship pre-human deities such as Ghatanothoa and includes hieroglyphs relating to the latter. There is also information on more recent cults including that of Bran Mak Morn, The Dark Man. It is from this work that the tale of the doomed heretic T'yog is most commonly sourced. The principal obscurity of the book is von Junzt's use of the word "keys"—"a phrase used many times by him, in various relations"—in connection with certain items and locations, such as the Black Stone and the Temple of the Toad (possibly associated with Tsathoggua) in Honduras.