"...I said I'd tell you. I don't have to assume horrible things about my friends to agree to tell you."

"All right. Well, I'm going to go see what I can do with this, thanks for getting it."

"I hope it works!"

And off she goes.

It does work, kind of. She can't use it with the teleportation form directly, but if she combines it with, for example, the light form, she can make something that points at the nearest magical thing of whatever sort. It doesn't have a range limit, though, so it'll do fine for what they want it for.

They're delighted and relieved to hear it.

And she gets to work. Worlds without people are rare; among those, worlds without magic - or at least without magic she can detect this way - are common. Worlds with people seem to be split about 50/50 on having magic or not. She keeps portal-enspelled notes on all of them.

So they should send some scouts to no-people-no-magic worlds, then, probably.

Yep. She comes up with a spell that'll notify them if there suddenly starts being magic - she wishes she had the form for spells that make noise, but she doesn't and they'd have to go to a human town for it and after the birdfolk she's not even going to mention it- and sets them up with defensive spells - there still might be hostile animals or whatever - and sends them off.

They have to come back near-instantly; can't breathe the air.

That's weird. Well, she can specifically aim for breathable air, she just thought 'presence of plants' was enough that she didn't need to; she redoes her world-survey with more attention to that sort of detail and gives them another place to try.

Yeah, seems like not all kinds of plants mean you've got the concentrations of air Quendi can handle. It's okay, they noticed and made it back in time.

Yeah. (Sorry about that.) She has specifically checked for that and a bunch of other things this time, though.

Cool! They go off scouting again.

The part of the world they find themselves in is warm and slightly swampy, with short, thick-trunked trees, occasional bushes bearing tiny flowers, and lots of ferns and mosses. There don't seem to be any birds or animals, but some of the bugs are quite large and elaborate. The plants smell nice, but don't taste very good - bland with an undertone of bitterness.

Well, they're planning to send Melkor here, not make it a tourist destination. They poke around for any surprises that wouldn't have been observable by portal.

Nothing obvious, at first. After a while, though, someone tries a magical song, and its effect is much stronger than they were expecting, and the magic detector keeps pointing at the spot where it was sung even after they stop.

...well. That. Probably isn't good. ...or, it could be good, but it's not good for sending Melkor here. 

Not so much, no. Well, Rána did have more places available for them to check.

They first want to check what happens if they try to use mage spells here, and what happens if you try enchanting a magic artifact.

Enspelled objects seem to work as expected, but if they try to cast a spell they'll discover that the process is both easier and harder; everything is more reactive, and it's easy to overshoot when they're trying to move things into the needed arrangements, but they'd also be able to set more sensitive trigger conditions more easily here. Enchanting is similarly affected; it's faster - not dramatically, but noticeably, even in a quick test - but easier to make mistakes if you're not used to the difference.

That is potentially useful. Okay, now they can head home and try for a better Melkor-prison candidate world.

The next world is mostly ocean, with chains of islands teeming with birds, bats, lizards, and other wildlife; a few hours into their visit they even encounter a pygmy elephant, barely the size of Huan. When they test it, their magic seems to all work normally.

That could work but what they really want is a world where their magic doesn't work at all. Any way to screen for those?

Uh. No, and if they do find one of those they might not be able to get back from it...

Ideally Arda magic doesn't work and they can't cast but they can activate a teleport. But that'd be a price worth paying, if.