A book relating to Iod and its worship, possibly from the planet Bel Yarnak. Its most famous form is a scramble of Greek and Coptic. This text was translated into English at least once, by Johann Nergus. Nergus rigorously excised many fearful matters of which he deemed it better that mankind should remain unaware. This is the only version of the text publicly known of, the single copy being held in the Huntington Library of California. An incomplete copy of the Nergus text was made by a man called Denton. One source claims that it is Gnostic work of some kind.
Lovecraft planned to mention the grimoire in his writing, (HPL: Selected Letters 4.828) but died before he could do so.