Brilliant post!, that I've only just found.
If these guys were a problem though, I'd imagine that people would have quickly moved to non-comestible stores of knowledge. Clay tablets would probably be my first choice, as they're cheap, easy to use and once baked, fairly durable. (bar the clumsy apprentice.)
If you have cheap metalurgy, you could also use sheet metal embossing to defend yourself from the niyotts.
I can totally imagine how a wizard's wealth and prestige could be measured by the instruments he uses to record his knowledge, with paper at the bottom of the ladder and magical crystals at the top, with clay and metal in between. Rich wizards could scorn poorer ones over their crude tools, while the gift of a crystal, or a sheet metal book, could be a right of passage in a magical academy.
Great post, that stimulates ideas and makes me want to roleplay an encounter with them.
Fascinating sub, (thanks to Kassy for pointing it out to me) and can make for a nice change of pace when used in an adventure, and a group of these is sure to be a mage or bards greatest nemesis.
I do feel the history portion fothe sub is a bit lacking however, why did this wizard create the Niyotts and send them forth to devour knowledge? Did he lose control of them or were they set free to run amok from the beginning?
Still great stuff, I can see these making an apperance in one of my fantasy campaigns someday.