"Still, we've proved that my magic can affect your harmonics in a useful purposeful way, which is pretty good for a day's work. Do you want to try the harmonics-affecting spells yourself?"

"One thing that I have been led to worry about is the risk of addiction. Is that a serious danger?"

"...It may be," she says. "I've never felt the temptation myself, but I've heard of cases. It can get pretty bad, and I don't have a good way to judge your particular risk. The sort of thing where either you'll be completely fine and never have to worry about it, or you'll be in big trouble, and there's no good way to know ahead of time which option you'll get. I wasn't thinking about it, but only because it's never been a problem in my tradition, and that's not all there is to it."

"Can you go into more detail on 'big trouble'?"

"People who get addicted to magic sometimes make very bad decisions about what magic they should be doing, and bad decisions and powerful magic aren't an auspicious combination."

"This concerns me. Is it a particularly hard problem to treat? I feel like I might notice from the first spell I cast if it were going to be an issue for me at all but if it is I'd like some sensible way to address it."

"The only effective treatment I've heard about is to never use magic again," she says. "Which I guess wouldn't be so bad starting from a position of never having used the relevant kind of magic before, but you might be in especially big trouble if your own magic turned out to retroactively become a problem, and I have no idea how likely that is..."

"I... had not considered the possibility that it might affect my equanimity with regard to sorcery."

"And now that I've thought of it I have no idea how to tell whether it's possible and how likely it is if so. Well, I suppose getting hundreds of sorcerers to try magic until some of them get addicted would give us an idea."

"I don't have any sorcerers handy besides myself. Mortals can learn it, but we have no addicts on hand to see if it satisfies the cravings. Do we?"

"I could try to come up with one," says Castle. "There are some people I could ask."

"And I think it would at least be challenging to come up with other sorcery to do based on learning how to make a fairylight, and those are quite harmless."

"So we'll see. But it might be prudent if you didn't try to do any local magic until we know what resources we have for predicting how magic addiction interacts with sorcery."

Nod.

Shrug. "Anything else I should test while we're here? Particular effects that it would be useful to know if local magic can achieve?"

"I wonder if you could let me sense harmonics directly. If it were a persistent effect it would be almost better than letting me flatten them out."

"I've been thinking about that," she says. "You might want to nominate someone else to test it for you, because it can be hard to reverse a well-cast chess magic spell, and it has occurred to me that a spell to see harmonics might not be able to function while leaving them unchanged, and you might not want to go around constantly scrambling harmonics in your vicinity even if it let you see them."

"Good points all. I wonder if Tea wants to see harmonics."

"Sure, why not," he says, appearing at the bottom of the stairs and looking up at Castle.

"The idea being that you may go around indefinitely drunkening or otherwise affecting them and this would be a good thing to know before casting it on someone who uses sorcery," explains Promise.

Promise supervises.

"Promise, would you like to participate? A second person sitting for rook will help to balance and strengthen the spell, and as far as I know the danger of magic addiction is only in the actual casting."

"Sure. What do I do?"