Cam sticks his wing out. "When."

Then he can be Acid Splashed. Anything?

A little discolored spot where the acid strikes and where it drips along the membrane of the wing.

It heals immediately.

"Oh, thank goodness," says Cam, rinsing the acid off with spontaneous water and re-folding his wing.

"I would be very careful about taking that as evidence that nothing here can hurt you." 

"If nothing else I don't expect to be immune to mindreading! But I do actually take it as evidence that your magic system does not bypass my indestructibility, which I expect to mean that it will continue to operate as normal."

"What's the biggest thing you've ever tested it against?" 

"Me personally not much but other apsels have tried a lot of things. Like, we can go hang out in stars, it's hard to get out again but it's otherwise not a problem."

" – Part of my intuition here is that the kinds of damage resistance I'm used to are uncorrelated. Our kinds of demons are resistant to acid and cold and fire but not, say, electricity, azatas are straight-up immune to electricity but have nothing against acid, devils are immune to fire and could probably hang out in stars just fine but are vulnerable to sonic damage. It sounds like our kind of magic is much more variable than yours, and magic users here have a lot of exotic ways to hurt people. There is such a thing as general resistance to spells but it works against mind-effecting magic just as well as physical damage, so I don't think you have it. Even if apsels are immune to every kind of damage known to your civilization, it seems reasonably likely to me that we've got some weird thing that could hurt you – and if you're going to help with our evil god problem, a lot of very clever people are going to be very motivated to find it." 

"I mean, obviously, as discussed, the weird thing that can hurt me is mind control. But I have fire and acid and electricity and loud noises and so on all covered. I guess if we do find something that makes more of a dent around here then that will be interesting information for suicidal apsels, who are currently kept strung out on their drugs of choice by volunteer caretakers."

"Acid Splash also isn't an ideal test, since it works by conjuring physical acid – it's just the one spell that does damage that I happen to have prepared. I'm – struggling to balance keeping information in reserve and trying to give you an accurate sense of how much weird stuff there is. Especially if you're fighting gods – sometimes they just decide to bypass all the normal types of damage resistance, or grant powerful followers the ability to do so. It's technically possible that you have some kind of ontologically basic invulnerability to everything except specifically mind control, but that would be betting really hard on mind control magic being a natural category and I'm not convinced it is. 

You don't seem like you're about to do anything wildly risky and I apologize for belaboring this point. I'm grateful beyond words you're willing to help with our evil god problem. I know a lot of people who've ended up dead and maledicted because they assumed they'd thought of everything." 

"I'm already dead."

"So are lots of outsiders. Just means that once they're destroyed, they're gone forever." 

"Well, that has never happened to any of the billions of daeva there are but if there were going to be an upset this would be it. If I get very spooked I may ask you to send me home."

"I can do that?"

"Probably? I'm in uncharted waters here."

"Why don't we circle back to my questions about how this normally works."

"On my home planet it is possible for anyone to, with a semester-long course or just a prewritten circle someone else designed for them, summon daeva, usually under a binding, though I am not under one now that I've noticed. We can then be offered trades to perform tasks; bindings can't make us do stuff, just make us not do stuff. Apsels make things, the other kinds change things or move things. That is the absolutely overwhelming majority of magic in my world, to the point where I worry you're going to get an inflated impression of how much other magic there is from the fact that I couldn't technically say 'literally all'. When we and our summoners are done with whatever we showed up for, they send us home. If the normal rules apply, which they may well not because as far as I know no daeva have ever been summoned to this planet before, you can send me home. I don't recommend that, since it seems as plausible as anything else that some of the normal rules apply, and you wouldn't be able to get me or anyone else back."

"Do circles summon specific daeva, or sort by type, or just grab whoever happens to be listening? does whatever I drew look like a circle you'd recognize? If I die, would you guess that you go home or that you're stuck here?"

"You must specify a type, you may specify an individual, taking summonses is voluntary. Your circle does not look like anything I'd recognize, I presume it manages to accidentally be a circle in some language neither of us knows, don't try it again, we can be mighty dangerous without bindings and apsels in particular are not filtered for friendliness by the summoning process. I would go home, if the normal rules apply."

" – Huh. We also have summoning spells that use magic circles to bind outsiders. There's a related class of spells that uses inverted circles – or maybe everted is the better word – for personal protection. The thing I was trying to do when I summoned you is modify one very, very common protective spell to see if I could get it to act like a slightly less common protective spell. Probably a few hundred thousand people know and use these spells regularly, that's probably been the case for at least two thousand years. If messing them up was likely to produce daeva, I'd expect to have seen the results." 

"Quite! It's not actually hard to wind up with a valid summoning circle for daeva if you are drawing circles on the floor and writing stuff near them. So, I think something weird may be up, but I do not know what."

"I've been worrying about that. It seems pretty plausible that something weird is, in fact, up, and there are lots of other daeva popping up in off-kilter summoning circles all over Golarion as we speak." 

"Hm, let me check."

Valid summoning circles completed on this planet in the last, hm, week?

"Looks like none this week but good to have checked anyway."

"That's good. You should keep checking. Can you show me what a normal summoning circle looks like? I want to see if it's anything like ours." 

"Can you reassure me that you are super duper clear on not doing this again without a more detailed explanation than a glance at a standard circle?"