Titivillus
In the Middle Ages, monks served as “printing machines.” They had to rewrite hundreds of books manually. So it’s no wonder that sometimes they made mistakes. Apparently, they didn’t want to admit them, so they made up a special demon called Titivillus.
Thay claimed that the demon collected every monk’s mistakes into a sack so that after the monk’s death the devil could show the mistakes and decrease the chances of being in paradise.