Featured on PDR in the collection The Key of Hell: an 18th-Century Manual on Black Magic

The Clavis Inferni ("The Key of Hell") by Cyprianus, is a late-18th-century book on black magic. Written in a mixture of Latin, Hebrew, and a cipher alphabet (namely that of Cornelius Agrippa's Transitus Fluvii or "Passing through the River" from the Third Book of Occult Philosophy written around 1510) the book has remained rather mysterious due to its unknown origin and context. It is said to be a textbook of the Black School at Wittenburg, a supposed school somewhere in Germany where one could learn the dark arts. As for the name of the author, it seems to have become a common name for people practicing magic. Benjamin Breen writes in The Appendix of how the existence throughout history of various magically-inclined Cyprianuses - from…