The largest medieval manuscript in the world was created in the early thirteenth century in the Benedictine monastery of Podlažice (then in Bohemia, now in the Czech Republic). This enormous work had just a single scribe — one Herman the Recluse. Handwriting experts confirm one hand was involved and a signature in the text (“Hermanus monachus inclusus”) also indicates that just one man — Herman — was responsible.

Why did Herman spend his days so painstakingly scribing? One version of the story says that Herman had committed such outrageous sins (not specified) that he was walled up alive and forced to inscribe holy texts to atone for those sins. It would take you about thirty years to write the entirety of the manuscript, so perhaps that’s true. If so, Herman did a lot of atoning.

Another version of the story says that yes, Herman had committed outrageous sins (again not specified) and yes, he was walled up, but this time the punishment was simply that he starve to death. However, Herman persuaded the abbot to keep him alive for a year and promised that in that time he would create a book that would glorify the monastery for ever. If Herman did so, said the abbot, he could live.

Herman the Recluse wrote day after day, night after night. As midnight of the last night of the year approached, he realised he was nowhere near the end of the book. Death at dawn awaited. So the enterprising monk blazed a trail others would later follow (Faust, Robert Leroy Johnson, etc) and sold his soul to the devil in exchange for a finished book.

It’s the second of these stories that gives the manuscript the name it is commonly known by. For while its official name is the Codex Gigas (in English: the Big Book; codex just means it’s a hand-written book), many more people know it as The Devil’s Bible. Partly because of the story surrounding its creation, partly because there is a large illustration of the devil within its pages. Put there, some say, by Herman as a thank-you to his satanic saviour. Put there, some say, as a selfie by Lucifer himself.

So why is The Devil’s Bible turning up on Planet Lost Manuscripts when it is plainly not lost? Because some of it is lost. The Big Book is made up of 310 leaves of vellum, but initially it contained 320 sheets. Who took out the ten other leaves? And what was on them?

At one point in its history, the codex was appropriated by the Swedes (responsible for other crimes in the annals of Lost Manuscripts) and housed in the Royal Library in Stockholm. In 1697, when a fierce fire broke out at the castle, someone strong and quick-thinking (more probably two of them; the thing weighs around 75 kilograms) thoughtfully rescued the codex from the flames by chucking it out of a window. Did some of the vellum flutter away in the fall? Probably not, as the National Library of Sweden states that the pages have been cut out, rather than blown away.

The rest of the book contains (in Latin, with rather lovely illuminated letters) the old testament and the new, a list of brothers living in the monastery, a calendar of saints, a short history of Bohemia, and some instructions on the exorcism of evil spirits. So the possibilities of what could have been on those missing pages are multiple.

You don’t have to trawl the web for long to discover various conspiracy theories about the lost content: secrets too explosive for mere mortals to know; magic spells; instructions for the apocalypse. Yet I suspect that the legend surrounding the creation of the codex is colouring people’s imaginations. The Swedish Library suggests that the missing pages contain the Rule of St Benedict, the founding father’s guidance on monastery life. Why? Because when the Benedictines of Podlažice fell into financial difficulties, they borrowed some money from the Cistercians in exchange for the codex. The note in the codex that records this loan also states that the Rule of St Benedict is inscribed in the book. So the Rule was there once, and now it isn’t.

There could have been other text, too (the Rule is quite short) but it’s likely to be a transcription of sacred words rather than a diabolic diatribe. We don’t know who excised the leaves, or why, or where they now are.

(In a recent fictional outing, on the podcast The Black Tapes, the missing pages of the codex are ripped out by Soběslav, Herman’s imaginary apprentice, who blamed the Benedictines for forcing Herman to sell his soul to the devil.)

In a way, Herman kept his promise — if ever he made one. The “inclusus” that follows his name in the text may indicate merely that he was a recluse who preferred a solitary life, rather than being forcibly constrained within brick walls. However, the legend tells that Herman promised to write a book that would glorify the monastery of Podlažice for ever more. Almost a thousand years later, we’re still talking about Podlažice, about his book, and wondering what was on its missing pages.

You can view the entire — and fascinating — digitised text of the codex at the website of the National Library of Sweden.

Codex Gigas digital images by Per B. Adolphson from the National Library of Sweden used under a Creative Commons Attribution 4.0 International License.