The Devil’s Bible
Also known as the Codex Gigas, this is the largest medieval manuscript in the world. The size is so big that it requires two people to lift it, and has both the old and new testaments of the bible, as well as books on the history of the Hebrew people and other histories of the world.
What makes this so mysterious is that there’s a giant image of a devil within the book, as well as, the writing is consistent throughout, suggesting that one person wrote it, over a possibly short time.