According to medieval folklore, the Codex Gigas was written in a single night by a desperate monk. The story goes that the monk broke his monastic vows and was sentenced to be walled up alive. To avoid this gruesome death, he promised to create a book containing all human knowledge in one night.

As midnight approached, realizing he could not finish the task, the monk made a pact with the Fallen Angel. He sold his soul, and in exchange, Satan completed the manuscript and added his own self-portrait on page 290.

Skeptics point out that a single person could not physically write that much text in a decade, let alone a night. Graphologists, however, have studied the handwriting. Astonishingly, they believe the entire book was written by one person. The script is uniform, with no signs of aging, fatigue, or changing style—even though it would have taken an estimated 20-30 years of continuous writing.

The manuscript, held at the National Library of Sweden (Stockholm), is not just “the Devil’s Bible” – it’s a complete medieval encyclopedia of monastic knowledge. Its contents in order:

| Section | Content | |---------|---------| | Old Testament | Genesis – Ruth (Latin Vulgate) | | Flavius Josephus | Antiquities of the Jews & The Jewish War | | Etymologiae | Isidore of Seville’s encyclopedia | | Medical texts | Hippocrates, Theophilus, Constantine the African | | New Testament | Acts, Epistles, Revelation | | Cosmas of Prague | Chronicle of Bohemia | | Martyrdom of Victor | Short hagiography | | Magic & exorcism | Formulas, including the famous full-page Devil portrait | | Calendar | Necrology (list of deceased monks) with lunar cycles | | Penitential | Confession guide & penance tariffs |

Translated from Latin, Codex Gigas means "Giant Book." It earned this name honestly. Standing 36 inches (92 cm) tall, 20 inches (50 cm) wide, and weighing in at 165 pounds (75 kg), it is so massive that legend says it required three monks to lift it.

But its size isn't the shocking part. It’s the content.

The book contains the complete Latin Vulgate Bible, but also the Antiquities of the Jews by Josephus, the Etymologiae by Isidore of Seville, medical texts, historical chronicles, and exorcism rituals. It is essentially a medieval library compressed into a single volume.

However, one page makes this book infamous: The full-page portrait of the Devil.

Likely written by one scribe in the early 13th century (Czech Republic). Handwriting analysis suggests it took 20–30 years of nonstop work — not one night. The “devil’s help” story probably spread later due to the unsettling image.