I have a friend who does absolutely beautiful calligraphy and she clued me in about the imp who causes problems with scribes: Titivillus. This creature is referred to as "the patron demon of scribes."
The best modern study of Titivillus is a scholarly one: Margaret Jennings's article "Tutivillus: The Literary Career of the Recording Demon," in Studies in Philology 74, no. 5 (December 1977).
Note: "Tutivillus: The Literary . . ." is not a typo.
Titivillus was a demon said to work on behalf of Belphegor, Lucifer or Satan to introduce errors into the work of a scribe. The first reference to Titivillus by name occurred in Tractatus de Penitentia, c. 1285, by John of Wales. Titivillus has also been described as collecting idle chat that occurs during church service, and mispronounced, mumbled or skipped words of the service itself, to take to Hell to be counted against the offender.
This goes beyond mischief, I think. Although perhaps Titivillus foreshadows Shakespeare characters such as Puck and Petrucio.