The next day is a Saturday; she wears the ring to the Avalon and is again only an ordinary amount of careless with it while she sits on a park bench working on a durability diagram and eats lunch at the Chinese place and so forth.

It persists in behaving itself when she checks.

She escalates to dropping it on the sidewalk, at some point when nobody's looking.

It bounces. It still works when she picks it up.

Brenda buys good materials. She goes back to working on the durability spell, with occasional breaks from stoichiometry to work on the incantation. When French ceases to be sufficient as a brain break, she walks around a bit. She has a general sense of the layout of the Avalon by now, but hasn't really seen most of the places in it aside from the library, the park, some restaurants, and Brenda's and Xavier's houses.

The Avalon has an arcade, a bookstore, a playground that looks like a poster for universal design, a community center currently in use for a lecture on Zen philosophy, a library, a professional-sized kitchen people can buy or subscribe for access to, a post office right near the entrance, stores which mostly have pretty limited selections plus ways to make special orders, a co-working space, a little park including a generic sports field in which some mad magical variant of polo is ongoing, a barber/groomer, a council building, a small black box theater advertising a run of "Cats" showing in the evenings and a few movies at various times during the day, a fortune-teller, and a one room schoolhouse.

. . . Margaret plays on the playground for a bit. Call it more wear-and-tear testing. She goes home before it's dinnertime, though, and by Sunday afternoon she has a draft of a durability spell ready. She's still following the "wait two days and check everything over" procedure, of course, and the incantation isn't quite done yet, but she'll be able to test it before game night rolls around. The incantation translates to "Make all components of this ring durable and strong against damage; let nothing break or alter them." 

Casting this spell does not kill her at all!

But does it make the wire of the ring harder to scratch up?

Yup, she can't get anywhere on that with the tools available.

She tries scratching the stone with her pliers, too.

Nope!

Excellent! Just for completeness, when her parents are in bed she'll take it down to the unfinished basement and whack it with a hammer, trying to break the stone. (Any warrantee she offers is not going to cover hammer-smashing, but she wants to know anyway.)

Her hammer bounces off and the ring goes flying into a pile of basement junk!

Whoops! Time to go fish it out. Maybe it's under the spare garden hose.

Yeah, there it is, totally unharmed.

Wow. She continues to love this magic system.

(Sadly, she is too ignorant of popular culture to make the obvious Lord of the Rings reference, so the narration is just going to have to allude to it.)

Does it still turn her invisible properly, after all that?

Yup!

Great! Except now there's nothing to distract her from the fact that she still has to figure out how much to charge. She goes back to the critter corners of the internet, and looks at all the enchanted object prices she can find.

Luck charms go for anywhere from seventy-five to seven thousand dollars. Vintage stuff and less popular oddball items are more expensive.

Hmm. Maybe eight hundred per, with durability and a warranty costing an extra two hundred? She can raise or drop prices later, if she can't get buyers or gets so many buyers she and Brenda can't keep up. She brings the (banged-up, scratched, amateurishly rewired, but doubly magical) ring and a few copies each of the invisibility and durability spells to Dungeons and Dragons. Onward, to get that box back to its rightful owner and maybe find out what's in it!

They get the box back to its owner! It turns out to contain a copy of the text of a prophecy which sure sounds like it could be what the cultists are reacting to!

Well, the description of the people who are supposedly destined to bring peace to two feuding cities could be said to match their party, but only if you interpret that one bit in a rather implausible way. It's probably not about them. What were they even doing before this whole mess started?

Escaping the desert. That's handled now. Joseph's character is spooked about the prophecy and attempts to suggest that the party hare off to his home country to do some things mentioned in his backstory.

On the one hand, bringing peace to two feuding cities is hardly the worst way they could be spending their time. On the other hand, if the prophecy is about them, it'll come true regardless, so why not hare off to Joseph's character's home country? Margaret is fine with whatever everyone else wants to do.