Herman the Recluse

Herman the Recluse (Latin: Hermannus Heremitus) was, according to legend, a thirteenth century Benedictine monk best known as the supposed author of the Codex Gigas, or Devil's Bible.

The legend states that, as a resident of the Benedictine Monastery of Podlazice, Herman the Recluse was condemned to be walled up alive and starved to death. However, in a plea for his life, he convinced the Abbot to let him live if he could create a book that encapsulated all earthly knowledge in one year. Herman wrote until the last night at midnight, upon which he realized he could not finish his masterpiece and sold his soul to a Tebel-El (Cornish word for 'Devil') in exchange for the ability to finish the Codex Gigas.

...
Wikipedia