Tanya nods, and follows her.

It's mushrooms again!

The local staple. Tanya dutifully eats her mushrooms.

And then Belmarniss thinks for a bit, and... Tanya's coming along on a shopping trip.

Tanya doesn't know yet that's what it is but she will come along! 

Belmarniss is talking to several people in a cluster of shops that sell rolled up paper and fancy ink. At one point she casts a spell and squints at a partially exposed bit of writing on a rolled up paper.

Paper is rare and expensive here, which makes it a luxury good and explains the fancy ink. You can make parchment from the pigs, which puts an effective ceiling on the price of paper...

Tanya has no idea what the spell does. (This is an inherently scary thought.) Belmarniss keeps it active after casting it but there's no obvious effect.

Eventually Belmarniss pays in gold for the scroll she squinted at.

It's weird how different worlds settled on valuing the same metal. Then again, it's weird how two different worlds settled on both having humans.

Then they're heading out to the suburban area where they met Johysis! And sitting in its library nook again! There are some drow children, about the size of twelve year olds, in the big open area all examining a diagram drawn on the floor in illusion colors of some kind while their teacher lectures and points at bits of the drawing with a long stick made of several bones fitted together.

Teaching is the bedrock of society and the fuel of the engine of progress! It's not a school class but it's a lot better than nothing.

Can Tanya figure out what it's a diagram of?

She can get an obscured view of it from a bad angle which probably suffices to tell her that it's a lumpy thing she doesn't recognize.

Oh well.

The illusion spell is also interesting! She can tell that it's an illusion but she doesn't understand how the spell works at all. At least she can record its shape and designation in her orb, as she does for every novel spell she encounters. (The orb isn't great at recognizing the local style of spell, but so far Tanya has encountered few enough of them that no two could be confused.)

It is also lumpy!

Belmarniss appears to be copying her new purchase into a big book.

...if paper is so expensive, it seems odd to copy things? A big book is undoubtedly more convenient than a collection of rolled-up scrolls, but you'd think someone would invent the binder.

Well, it's gonna Take Her A While. She does occasionally pause and look up in case Tanya's state has changed.

How long can it take to copy a single scroll? It's not a very long scroll. She must be doing something other than simply copying it, but Tanya will have to wait for an explanation, if it's even something to do with her or their business together.

Tanya can wait a While without fidgeting!

If she looks at the scroll it is in fact covered in really fine drawings and complicated legends and arrows and symbols, and it's not being copied verbatim (it has to go across more than one page of the book, for one thing, not a continuous stretch).

When the process is finished the scroll goes suddenly blank, the writing receding into nothing from a point in the lower middle.

Is that perhaps information on their route? It's a very dense notation, whatever it is, and it makes sense if Belmarniss wants to simplify or annotate her own copy.

Cleaning the precious paper for re-use is very sensible except - how did she do that? Tanya did not sense any magic! Did the other woman's presumed-illusion spell also do this somehow? Was it a trick some kind of vanishing ink? The receding effect did not look like a natural progression of the ink vanishing, it looked like computer graphics an illusion. If local illusion spells can produce illusions at least some parts of which don't seem magical to Tanya then she's going to be in danger - no, that makes no sense, why would she do that. 

Nobody in the room looks surprised (except for Tanya). She will ask Belmarniss about this later.

The scroll gets rolled back up and bagged. The book is then... studied carefully even though she literally just wrote it down?

Maybe she's committing it to memory because the book is heavy and precious and shouldn't be taken with them?

Once she has been at this step for fifteen minutes she casts something and the book vanishes in a somewhat showy sparkle of lines and sigils that promptly vanish with it!

Um.

Is it another illusion? There's no lasting magic and also why would she illusion the book gone. Surely she did not destroy it, even if there was a... book-destroying spell that looked like that. This is... presumably related to the weird-looking ink-destroying (???) effect from earlier, except that wasn't even magical!

Whatever the spell did, why did it produce those sigils? ...she's being stupid, they're obviously meant to tell locals what the spell is doing. Very sensible when one is not in the military.

Tanya now has More Questions.

Hand?

What - oh, it's probably the language spell from yesterday or something similar. Sensible to keep it until Belmarniss was done with her business, since it doesn't last very long. She thinks Belmarniss can't cast that spell, so probably it's another spell with a similar framework?

...it's a very civilized and admirable convention, whether it's magical in nature or merely social, that to cast a spell that affects another person you must shake hands with them. Tanya approves. She will take Belmarniss's hand.