There have been many grimoires attributed to St. Cyprian of Antioch due to his reputation as a skilled magician before his conversion to Christianity, but perhaps none so intriguing as the present unique manuscript. Although it is highly unlikely that the text is by the historical St. Cyprian, this does not detract from its extraordinary contents. This is a full reproduction of the text of Wellcome MS2000, together with the translations of the Latin texts and commentary by Stephen Skinner and David Rankine, who worked for many years, sometimes with the help of other esoteric scholars, to decipher the coded writing, scripts and symbols found throughout. Clavis Inferni is a unique text which will be of interest to all scholars interested in the magical grimoires, as well as modern magicians who have an interest in working with Metatron or the Demon Princes. The material is largely derived from the Heptameron, so continues a rich magical tradition.