Shadow

A wizard summoning an Unseen Servant in an untidy workshop unknowingly made the summoning permanent. So, Shadow wandered off to have a life of their own.
They have a tendancey to absentmindedly follow any orders they are given, but can snap themself out of it.
Shadow has an innate affinity for books and reading, and dislikes the hoarding of knowledge in private libraries. They often sneak into such places to copy down books.