"It cannot be done remotely. It - could, probably, be set to trigger on a short delay, time enough to Gate out." 

" - I don't think that's worth it, but I appreciate knowing the option. The big challenge will be that we need to get someone to Dis to deliver the weapon. One way to do that is to fight through the guarded entrances in Avernus, that's the only way with my world's magic, but it's possible that by the time you've developed a powerful interplanar Gate it'll also be possible to use the powerful interplanar Gate to get from Avernus to Dis, in which case - I would ask someone to do that. The less warning Hell has, the better."

"Does the planar boundary block your world's form of transport magic? You have one, right?" 

"Yep. You can only - using our magic - get to the second layer of Hell via locations on the first layer which are guarded. Heaven works the same way."

Nod. "It sounds unfortunately difficult to study, or - check in advance - unless the first layer can be infiltrated without being caught?" 

" - not impossible but I'd rather not risk it without good reason to hope it'd work; we probably lose everything, if Hell suspects too soon."

Nod. "I assume the same barrier would prevent us from scrying it from here, or from the ordinary material plane of your world? If there is anyone who has memories of Dis, that could be shared with Thoughtsensing, a reasonably experienced mage could test it quickly at the time - if we do not have that specific to aim for, I think I could still do it, or Ma'ar could, but it sounds - risky."

Sigh. "And that is probably getting ahead of ourselves, when we do not have interplanetary Gates yet at all." 

"Once we have them there are additional researchers I can bring in. And - maybe someone with memories of Dis, maybe worth a True Resurrection to get someone who has those - but I think none of this changes that our first priority is interworld Gates and contact with our world."

"- You can do that? I - how -" 

Urtho catches himself. "Right. Of course." 

Ma'ar has some initial ideas to try to explain - he'd rather do it while he's wearing the headband, it makes it a lot easier to turn wordless intuition into explanations - and then they can head to a Work Room and Urtho can take the headband before running some tests on planar interactions.

It's not spectacularly safe, but Iomedae is very close to indestructible and it's probably not an issue for her to be in the room (though their discussion is very quickly going to become incomprehensible to her.) Ma'ar appreciates having her there. As long as he has the no-fear effect, he is basically not stressed about working with Urtho, and hopefully that lack of stress will stick later. 

Iomedae is happy to do her thinking-through-assaults-on-Hell in the room where the wizards are doing magical testing.

The headband is GREAT and Urtho is going to use it entirely for magic research, which is fun and exciting, and not for thinking about his life, which is much less fun and exciting and is something he can do after they have a plan to destroy Hell, which is a lot more important. 

They make some progress! Not a lot of progress, it's going to be at least another week of work, but Urtho has some promising theories on interplanar routing. 

And Ma'ar has some ideas for routing the search to look for artifacts like Iomedae's. Are any of hers ones that would be standard and common in her world? 

Most of them, actually! Not the headband, and not the armor, but most of what she's wearing is the ordinary equipment of extremely scary people.

Then those seem like promising search-spell targets! 

...The naive approaches, unsurprisingly, do not work. Iomedae's world is very far away. But with a headband to trade between them, and Iomedae's artifacts to study directly, and Iomedae right there to consult on some kinds of questions - to the extent she knows anything about, say, how summoning elementals behaves in Golarion - they can make steady progress most days, in between juggling their other responsibilities to their respective countries. 

It takes nine days, and a couple of false starts until they figure out where their models of planar interactions were wrong or incomplete, and then they have a scrying spell!

Urtho thinks it should probably work. The power requirement will be very high, it's going to have to be a concert-ritual the first time, but once they confirm they've found the right world, he can refactor the routing and get it down to something an Adept can cast alone. 

Does Iomedae want to be there? (Urtho isn't a Mindspeaker and can't share what he's seeing directly, but it's not that much extra work to set up a visible illusion and show everyone.) Also, is there anything he should be particularly careful of? 

Yeah, they want to not scry Tar-Baphon, though he shouldn't be a valid search-target because he has a Mind Blank and she's picked magic items he doesn't wear. They also probably want to not startle Iomedae's allies, for the same reason, but she expects that the typical wearer of a Ring of Sustenance like hers is a well-to-do noble or retired adventurer, and importantly definitely isn't undead.

(She'll have a Magic Circle Against Evil up while they're casting just in case. This will protect against Domination by Tar Baphon and....proooobably also protect against it from Alfirin.)

Great! Then Urtho will summon a dozen of his best concert-trained Adepts to a specialized Work Room, where they can use the more flexible (if much less power-efficient) scrying artifact he's thrown together for this purpose. He'll do a better one later. 

Ma'ar is not really trained in concert work up to Urtho's standards but is invited to participate, he's a Mindspeaker and can probably pick it up fine? 

Taking down enough of his shields to join a meld with, not just Urtho, but a random subset of the mages directly loyal to Urtho, is actually super nervewracking! He can do it if Iomedae is there and can do the no-fear effect so he doesn't keep flinching about it. 

Iomedae will absolutely do the no-fear effect, in addition to her Greater Angelic Aspect which does Magic Circle Against Evil and a Lesser Globe of Invulnerability, and a Prayer to give everyone good luck, and also her she's-not-even-sure-if-it's-magical ability to just make her allies succeed at whatever they're doing.

In that case Urtho will get his scry through on the first try! 

It's going to land on a semi-random instance of someone wearing a Ring of Sustenance, though weighted toward whoever also has the most total spellsilver and artifacts on or near their person. 

Then it'll land on a lead spellsculptor - not important enough to be under a Mind Blank but important enough for a ludicrous amount of magic jewelry - in the Empire of Shu, actually!

He doesn't observably notice; he's working on magic item crafting, it looks like.

That is the most beautiful thing Urtho has ever seen in his entire life!!!!!!!! Urtho is maybe tempted to hold the spell until everyone's reserves are drained, just to watch more of the crafting. 

...Does Iomedae think it looks like the right world, if it's somehow the wrong world with similar magic then they should drop it now to try again. 

Looks like the right world to her.