I really want to talk to the Druchii, first to know what they're doing right now, second cause I think the possible trade with the Sorceress is a good idea that would benefit us and the whole Old World than it would benefit her. To name a few of the things we could get from Sorceress Myrielh and tried to give a little argument about why we might want them:
-Books and information about Enemies of Men (Orcs, Skaven, Beastmen, etc.): Useful information to have that could help the Empire, and most other nations really.
-Books from Nippon or Cathay: extremely rare books to get, we may end up getting Cathay books somehow but otherwise I doubt we'd be getting Nipponian ones. At the end of the day these are more bonuses for KAU and very rare books which we may leverage to obtain rare books from other libraries.
-Books and information from Lustria, from terrain, to lizardmen, to maybe a Saurian lexicon: the Empire seems to lack a lot of info about Lustria and this could help patch that hole and maybe, just maybe, manage to keep the poor mayor of Swamp Town alive.
-Books and information about Albion: we know one of the Gray Lords knows about it (although they didn't tell us anything). So it stands to reason they would know too and with a bit of luck we may be able to get some info from them.
-Books and information about Ulthuan; honestly I am just curious about what the Druchii would have written about Ulthuan
-Books about Naggaroth in general (society, geography, history, gods, etc.): They'd be extremely rare books in the old world which we could leverage with the cult of Verena for books they have. This is most likely the only chance we'll ever have to obtain them. I am also curious about what the Dark Elves have to say about Hekarti.
-Books about True Dhar: Probably hard to obtain and after a certain point most likely sabotaged, but regardless of the sabotage these would books would contain how Druchii sorceresses learn and cast magic so they'd be great to learn to counter-spell them. Also it might be a good idea to get these before either Elfication in case we have to fight some Druchii sorceress.
-Books about High Magic: probably one of the very few sources of High Magic books. It's a good chance to learn what High Magic is and how it works and maybe help us with Windherder. Most likely these won't be tampered with as the Druchii don't do High Magic and their value would come more for them to be able to counter spell the Asur.
-Books about other exotic magics (Gut magic, goblin magic, Cathay Magic, etc.): Just more books about magic. I doubt they're tampered with in any way since Druchii don't use these magics.
-Books about Chaos: On one hand, a chance to learn more about Chaos and Chaos sorcery and how to better fight it. On the other Chaos.
-Common books from Naggaroth (example: textiles): just more rare books for our library which is always nice.
Also there's the fact that we could get books about the winds of magic. They are most likely going to be tampered with, but we can just stash them away until we can get a Grey Lord like the one who flexed on the Sorceress to take a look.