Quote Originally Posted by Quertus View Post
If the books you're reading weren't written by the future people and brought back via Teleport Through Time, or by people asking questions about the future through Divinations, your world is suboptimal.

Color blue to taste.

(I'm not a fan of Knowledge skills. No, I've never made a character whose backstory was that they were reading their own (temporally-displaced) journals as the excuse for their knowledge skills, why do you ask?)

(Quertus, my signature academia mage for whom this account is named, isn't reading books - he's writing them. Much more fun than making knowledge checks, IMO)
Those sorts of libraries do form a particular trope.

I could definitely see something where, if you happened to use a particular library as a magical location to do your research such as the Library of Leng, Thoth's Archives, or the Akashic Record, you could e.g. capture even unknowable things with Knowledge in exchange for, say, the loss of 1 sanity point per 5 points of your Knowledge check result...