"Mighty adventurers are best for mana production. A world-city packed like sardines would have a hundred times the people, who produce a hundred times less on average."

"Huh! What about the adventures changes people?"

"Tch. It's not like I'm an expert. Something about the stress, achievement of mighty things under dangerous conditions, that flash of insight and triumph when you overcome a peril, and all the murder."

"...have any unethical researchers tried doing the murder by itself?"

"I suggest you do your research on this on your own time, it doesn't interest me."

"Fair enough. What happens to spent mana?"

"Mana is technically negative entropy, I told you this earlier. Spent mana is equivalent to the mana field ending closer to the magical equivalent of lukewarm dust."

"Entropy is often like heat, right? Waste heat? Is there a mana equivalent, that can in principle be captured for further use?"

"Certain uses of mana are more efficient, theoretically there is the possibility of perfect efficiency - one to one state conversion. In principle yes, many inefficient mana engines produce 'waste' that can be 'siphoned'. Slimes are known to do this, especially, slimes are an utter pest around badly cast magic. I have, as I told you earlier, a book on it that you may borrow. Later."

"Okay."

Back to the lecture then! Loril has an auditory metaphor for bindings, but knows the visual ones as well, since she (rarely) works with other motemancers. And the textbook has plenty to say on the topic as well. Another hour and they work on a decent introductory understanding of the mechanics of applying bindings and what they'll do. Of course, the trick is the details. There's going to be a lot of practical effort as well.

And then she announces a ten minute break and her intent to go grab a snack.

"Sounds good to me too, can you like, nudge me with the portal if my time sense is completely off, I don't seem to have been instantiated with a watch."

"Yes, yes, very well. By the way, you will find that - so long as training continues - you are able to open a portal here at any time."

And then she marches into a portal that appears before her and vanishes just as fast. All that's visible in the second it's open is a voluminous dark curtain.

Bella goes back into her dimension and checks out the contents of the kitchenette. Does she like, place orders, or do random things just appear?

Her cabinets will always be at least partially full of semi-random staples and raw produce/meat when she needs it. One of the cabinets is a fridge/freezer combo. She can make specific requests on a special note pad but that costs more mana. Which the Khintal-paid maintenance might not cover.

She rummages and comes up with a celery stick and some peanut butter, that's a fine snack. Applies the one to the other and munches and heads back to the training plane.

The quiet guy, Nicholas, is waiting nearby when she does.

"Hey. Bella? Just want to tell you that... Loril isn't mean, just bad at social. She grows on you. Or me at least. Um. Anyway, yeah, that's it." He shrugs and starts turning away back to his rock pile.

"Good to know. I don't mind her really, it's just an all-business interaction and that's fine."

Bella claims motes. Can she independently figure out what color makes the rock pliable?

The book told her what colors to use, in fact, though it's slightly trickier as you have to make half this color and half the other. It may take a couple of attempts to get right.

Ooh, hm... can she start with the motes near one hand as the first color and the ones near the other as the second color and then kind of diffuse them into each other?

Earthmotes don't really want to diffuse that easily. Also, what ends up happening is that one side of the rock becomes almost liquid and runs out of her hands.

Huh. She resumes practice with the smaller half of the rock. What happened to that one, anything?

Bits of stone stick to her 'skin' and harden again.

The remaining rock doesn't seem any different?

Heh. She liquifies the stuck-on stone and shakes it off.

Does the book say anything about what the colors she's supposed to mix do individually, is this rock secretly structurally weird in some way now?

The first color reduces earth's cohesion with itself, while the second color increases hardness/stiffness/brittleness.