It's sort of like having high stakes treaty negotiations conducted by a small child. An alien small child made of magic from another world. Savil is really really unsure what to think, but she's pretty sure, at this point, that the creature calling itself a lantern archon is not going to hurt them and is, in fact, probably not capable of hurting anyone deliberately.

Finally she thinks to ask. "Can we cast a Truth Spell on you? I don't know if it'll - work - on your kind of being, but it's a kind of magic we use very commonly here, when there's an important message like this." 

"Yes definitely! I think it will work. Truth spells that use our kind of magic work on me."

Savil casts it, calling the vrondi to hover near the archon and attempt to sense its mind and intent. She waits to see if the characteristic blue halo will appear. 

It does! The lantern archon seems to notice, and shifts its own coloration to match, and bounces a bit more.

It's very cute and she should definitely not let that shift her sense of its trustworthiness, this could still be - what, manipulation or misdirection of some kind? It's pretty uncontroversially proof that there is another world. It remains unclear how Vanyel actually ended up there; what he told her during his mysterious Mindspeech-from-nowhere message might be the truth or it might not be. All of this is bafflingly weird. 

"Can you repeat everything you said about Vanyel, please," she says. 

It repeats everything it said before about Vanyel verbatim.

Nod. "Thank you. Did you meet him yourself?" 

"Yes! He was not my summoner but he was in the room, and he sent me an image of Haven in my head so I would know where to teleport to because Plane Shifts are very inaccurate and can put you very far from your destination."

That's an interesting fact to know in itself. "Can you describe how he, er, seemed to you? Did he seem well?" 

"He seemed very tired. I don't know much about mortals though. I think he was a little worried that I could not do this."

"That you couldn't...what? Not scare us? Explain what you explained clearly?" 

"I found the explanation quite clear," Shavri says, in a tone meant to be reassuring. 

"Explain things clearly so you weren't scared and so it was okay for them to wait until the gods say they can come here. And so that you don't get turned away from the forces of Good and Law though he didn't mention that particularly but that's the usual reason it's important to be really really good and smart on other planes, so people see that the forces of Good and Law are worth protecting and fighting for."

There are glances around the room. 

"None of us are at risk of being 'turned away' from law and good in general," Savil says. "Although it - still sounds like it means something different, in Golarion, from what we mean here. Can you describe a bit more what it means that the forces of Law and Good would come to our aid if we were threatened? What would that actually look like, and how would you, er, know, that we were under threat?" 

"Well, I could stay here and maybe explore a little bit if you didn't mind and then if you were under threat at some point you could tell me. The Outer Plane I am from is the Lawful Good one, and it has armies, and we fight Evil, wherever across all the worlds it is necessary. And it works extra well to fight in places where no one knew you existed or how your magic works because they will be very scared and maybe decide not to fight after all, or at least not be any good at it. So if Valdemar were under attack by evil, you could tell me that my task is completed at which point this summons will end, and I could go to the strategists for the armies of Heaven, and tell them you need them, and then they'd come here and figure out how to help. We have hundreds of thousands of soldiers, in Heaven, and they have very powerful magic."

...Well that's terrifying. It would also be reassuring if it were definitely true, but there are enough layers of uncertainty there that finding out about a foreign world with a powerful magical army is mostly aaaaaaaaah. 

"Does the army stick around and occupy a place afterward?" she asks. 

"No! Conquest is Evil. It'd also be bad for Law but in a more complicated way -" the light concentrates inward - "Oh! I have it. So if you were pushy with your allies then no one would want to ally with you and that's the shape of things that matters for Law. If people aren't sure they want you as allies then you're doing Law wrong probably even if you haven't broken any specific terms of any specific agreement."

"Oh. Yes, I understand what you mean. Our country tries to do a similar thing." 

The room is silent for a bit, thinking. 

"Can you show us your magic?" Savil says finally. "All of the kinds you have, please." She's going to feel a lot more comfortable letting this weird adorable alien creature explore if she knows that none of its magic will hurt people, even by accident. 

"I can teleport anywhere." It teleports across the room. "I can detect evil. I don't think that will look like anything to you, I am doing it all the time. I can give people some extra energy, temporarily, but it wears off after a couple of minutes. I have to touch them to do that. And I can fire beams of holy light but if I do that at people it will hurt them so I think maybe I shouldn't."

"Please don't do that! Er. How badly does it hurt people." 

"I have never done it to mortals because I think it could be quite bad, if you got unlucky and hit them just wrong. It doesn't hurt the armies of Evil very much, you'd need dozens of us to teleport over all at once and attack together to accomplish anything. - I have never done that either but I've seen it."

"I see. Can you, er, promise not to do that at all here, unless we - decide that we want to ask for the armies of Law and Good, in which case whoever is in command should talk to us before they do anything."

"I promise not to do that at all here! If you decide that you want to ask for the armies I will tell them that they should talk to you before they do anything! I think they would have to do that anyway since it is your country and you probably have laws about people in your country hurting people and we cannot break those."

"...You can't?" Shavri says, a few beats later. "Or don't? Is it that you have a rule against it or is it more of a 'can't' than that?" 

“We can’t do unlawful things no matter what.”