Margaret doesn't usually have magic accidents. But this time she was holding her whole rune dictionary and also an unlabeled thing she found in the magic shop, and she really wanted to see what the thing did as long as it wasn't fatal, and now she is somewhere unexpected. If it turns out that the thrift shop thing was a teleporter that'll be kind of disappointingly redundant but not actually a problem.
"It's gone up a lot in the past century, yeah. And magic is kept secret by being careful not to do any in front of someone who doesn't already know. There are magically hidden towns where people who want to do a bunch of it live."
Margaret wonders if it's in some sense illegal to explain that, but this person clearly knows about magic and Margaret is legitimately uncertain as to her species, and also if they don't swap magic explanations how are they ever going to get to the bottom of this.
"Some people used to be able to make the inside of a building or a cave or whatever bigger than the outside, so you could fit a whole town in one building. Nobody has made a new one in a while; the knowledge got lost."
That gets her a boggle-eyed stare, and some mutters with the others. "That - is not possible given what we know of magic," the mage says. "Even in principle, I think, it is not just that we do not know how - unless it is a somehow Gate to another plane, I suppose, does that sound right...?" She seems very doubtful that this would make sense.
"I don't think so? I don't know enough about Gates to say, but I think if there was an earthquake near an Avalon they'd still feel the shaking. Also we don't have any other way of interacting with other planes except I guess the thing that sent me here."
She can describe it's physical appearance, egg-shaped with a pushable button, and that she got it from a magic shop and the owner of the shop didn't remember where he had gotten it from, and that most magic items that turn up abandoned and unlabeled in shops do either nothing or something pretty trivial.
"Not as a magical matter; most of them have rules about who's allowed in but anyone can physically go through the door."
"The magic store was in one of the towns that had that rule. I have some magic but I don't know if it works here." Probably any of it does or she would have appeared in fullform, and wow is she glad that didn't happen. "Um, side question, does this planet have the concept of people who can talk and stuff but aren't human?"
"Okay. My world has more species than that but only humans are common knowledge."
"I can do that, but doing anything new would be potentially dangerous and also require hours of prep work. I can try testing the artifacts I have on me; I have a ring for invisibility and one for teleportation. I could turn invisible for a few seconds and then turn back?"
The woman nods. "I'll watch you doing that. I - mainly want to see what your magic looks like, to us, and how different it is." (This seems like a good way of checking the strange woman's story about being from another world somehow, as well as getting more information about whether she's a threat.)
"Okay, trying it now." She says an unfamiliar word and disappears (to ordinary vision; it's clearly visible to Mage-sight as a brief flash of magic from one of her rings), then reappears with a different word and another flash of magic a few seconds later.
"Turning something into a magic artifact requires drawing a really precise diagram and speaking a precisely-worded incantation and then it works from there. For a bigger effect you need a bigger diagram so I think the power comes from the runes somehow. Spell effects that aren't attached to an artifact wear out but ones on artifacts last a long time."
"Yeah, I think we just have completely different stuff going on. I actually have a book with a bunch of runes in it; I was holding it when the artifact sent me here." She pulls the book out of her biggest cargo-pants pocket and opens it to a random page. Each rune has a shape, with the lengths of lines and the angles between them labeled, and a list of meanings like "fire" and "border" and "life" that the runes have different amounts of. "Also, actually doing anything with runes is really dangerous, like lots of people have died trying it dangerous, so please don't go experimenting."
"That doesn't surprise me; they only do anything when written in the right kind of arrangement and spoken at with the intent to do magic."