This thirteenth century Grimoire is one of the foundation works of European magical practice. It was one of Dr. Dee's sources for the Sigillum Dei Aemeth.

The Sworn Book of Honorius, or Liber Juratus (also liber sacer, sacratus or consecratus, Sworn Book of Honorius, Grimoire of Honorius) is a medieval grimoire. Its date of composition is uncertain, but it is mentioned as liber sacer in the 13th century, apparently asserting a high medieval date. Johannes Hartlieb (1456) mentions it as one of the books used in nigromancy. The oldest preserved manuscript dates to the 14th century, Sloane MS 3854 (fol 117-144). Sloane MS 313, dating to the late 14th or early 15th c. had been in the possession of John Dee. The book is one of the oldest existing medieval grimoires as well as one of the most influential.

It is supposedly the product of a conference of magicians who decided to condense all their knowledge into one volume. In 93 chapters, it covers a large variety of topics, from how to save your soul from purgatory to the catching of thieves or finding of treasures. It has many instructions on how to conjure and command demons, to work other magical operations, and knowledge of what lies in Heaven among other highly sought information. Like many grimoires, it has lengthy dissertations for proper operation and seals to be used.

The book can be classified as a "Solomonic Grimoire" due to its heavy use of angelic powers and seals like those found in The Greater key of Solomon. {Description courtesy of Wikipedia}