The Pnakotic Manuscripts (or Pnakotic Fragments) is a grimoire created originally by the Great Race of Yith and kept in their library-city of Pnakotus.
Roughly 1,011 (MXI) fragmentary manuscripts making up several books, sometimes called Pnakotic Fragments. The manuscripts seem to have started as the “pre-Pleistocene” records of the Great Race, they were later added to by the prehuman worshippers of Tsathoggua (the Voormis) and then by the Pnakotic Brotherhood, right up to the flight from Lomar, when copies were carried into the Dreamland, among other places. Each generation of the Brothers added to the text. The eighth fragment deals with Rhan-Tegoth. In the 15th Century the one public translation (into English) was made by an unknown author. This “pirate” version is known only as five bound manuscripts held by major libraries in Europe and America.
Behind the Mythos
The Pnakotic Manuscripts were created by H. P. Lovecraft; and extensively expanded by Lin Carter, who wrote a couple of "chapters" from the work; Chaosium has also added data.