A fragmentary and inaccurate translation of the Latin Necronomicon into English by Frederic the First (Fredericus Primus), Baron of Sussex, perhaps more correctly called Cultus Maleficarum. It appears to have been printed in Sussex, England, in an octavo edition in 1597 C.E. The original illuminated manuscript is held by the British Museum. The Sigsand Manuscript is sometimes mistaken for this volume.
References to the Sussex Fragments seems to refer to the shards found by the Rev. Brooke Winters-Hall in 1912 and is not, therefore, an alternative name for this volume.
Behind the Mythos
Created by Fred Pelton, who wrote an illuminated manuscript version. Derleth considered publishing the book, and so referenced it in his stories to drum up interest, but eventually dropped the plan. As a result Pelton's vision of the Mythos was sidelined and now conflicts noticeably with the Mythos as it has developed. The text was finally published in the 1990s and so some influence has now appeared in the fiction.