This is related to my last question here.
The library here is not necessarily the magical sentient library mentioned in the previous question, but can be any wizard library. This library can be in any form e.g. a secluded tower in a wood, or a huge library where many wizards live together, or in an academy.
This parasite is an obligate parasite: it cannot live outside a wizard library, or it will die in 2-3 days. The parasite can be found in virtually any wizard library, and even an apprentice mage can detect its presence.
Considering it is a parasite, and it often tampers with a wizard's experiment or spell casting:
Why do wizards not attempt to exterminate these parasites?
- The parasite feeds on remnants of magic power used from experiments or spell casting. Often, it intentionally distracts the caster so that the spell fails, to get more magic remnants.
- There is no mana required to cast a spell. The residue of magic power is only produced after spell casting.
- There is no benefit for a wizard or mage to keep this creature around.
- This creature can accidentally activate scrolls. However, it is not believed that it does so on purpose. It might be on purpose, but it has never been proven. Scrolls can be activated without knowing the inner workings of the spell.
The physical or magical features of this creature are up to you to decide, but I'm imagining a ghost-like semi-corporeal creature flying around the library. You can make up a fully incorporeal ghost, or something like that.