Then Merrin can fill Estha in on what equipment she arrived on this planet with, what sorts of training she has for using it, and what she's done with that so far to survive! 

There are some obvious disconnects and Merrin ends up having to jump back and fill in a bit about her training, which did not involve learning how to use [spells] as a [cleric] of a [god]. Instead she trained as a medtech and had a normal hospital position - she'll have to digress briefly here to explain what a hospital is and why it makes sense in a world without any kind of [cleric] [spells] for medical treatment - and at some point it came up that she has unusual stamina, and so despite the fact that she's rather lower - huh this language has bizarre buckets for mentalabilities - anyway she's presumably below average on all of them, but she can train harder to make up for it, and for some situations there are very significant efficiency gains from being able to dispatch one medtech who can proceed to work for twenty hours without falling over, and so Merrin transferred to a position with Exception Handling and has, since then, done a mix of simulated-emergency-response trainings and actual emergency response calls, plus some number of regular hospital shifts so she doesn't forget the basics... 

...Merrin does not think of her scientific knowledge base as unusual. If anything she clearly thinks of herself as a bit dull. But she knows the basic established dath ilan science about, say, planetary orbital dynamics, and some very basic programming and very basic math and very basic structural engineering to design her shelter, etc etc, and she knows more biology than that even when it's not strictly speaking human medicine, so she was able to make some reasonable judgement calls on testing edible local biomass... 

Several things will likely be apparent to Esta: 

1. Merrin really, really loved her work with "Exception Handling".

2. Merrin does not say as much, but it does not, really, seem like her position as she's describing it was very equivalent to a 2nd-circle cleric and Worldwound fort commander. It sounds more analogous to the sort of person who would have been alongside Esta on the 7th-circle Worldwound emergency response team, albeit for different and fairly specific types of "emergency"; dath ilan is coming to sound like a place that has fifty different such specialized teams, and Merrin would only be assigned to a few of them. 

3. Merrin does not really at any point acknowledge that this might be notable. 

If Esta was not thinking of all this in terms of "Dark Tapestry inversion" it is possible that it would occur to him to wonder if any of these ideas would work on Golarion and could be sold for big money or parlayed into some sort of military advantage.

Esta has not usually been instructed to think in that general direction!  He has been rendered more corrigible than that.  Possibly if Esta had a superior present, Esta would ask them whether to think in terms of exploiting all this knowledge, or for that matter, trying to mine diamonds on this untouched exoplanet.

But this is not where Esta's attention and concern is pointed by default.

If Esta had heard all this, one hour earlier, it would have occurred to him to wonder if 'Merrin' is perhaps, somehow, a completely alternate version of Mariona from some kind of shadow of Golarion; whether Mariona was outright replaced and not just inverted.  For much of this does not sound like a direct mirroring or inversion in particular, and parts of it do not obviously match up with his remembered Mariona at all.

Thankfully, Esta has by now seen the key piece of evidence which contradicts this.

Because if Merrin was really from some entirely different world, related to Mariona only by some strange coincidence of appearance, or magical shadowing effect --

-- then why would that country -- or perhaps entire planet, for there is no mention of distinct countries, in her words, or even distinct cultures --

-- why would that whole country have a rule specifically saying not to tease Merrin about her future potential if she ever acquired ambition, as Esta specifically teased Mariona about, and Mariona specifically hated?

And the answer is that it would not.

New hypothesis:

The whole world that Merrin thinks she is from, is in some sense a shadow cast by Mariona.

There are other signs, in her story.

Esta's first domain ability from his Devil domain was "Hell's Corruption", a transient touch of evil upon a soul, like some vastly lesser form of Malediction, which makes a being "more susceptible to corruption" by bringing up its repressed desires.

It sounds a great deal more awesome than it actually is.  In practice, you land a touch attack on an opponent, and then they'll be very mildly distracted by all their repressed desires welling up, for a number of moments equal to your cleric circle.  So far as Esta knows, not a single paladin has ever fallen as a result of being so touched, in the history of Golarion and maybe of Creation.

They warn you, in seminary, if you have the rare Devil domain, that "Hell's Corruption" really really is not as useful as it sounds.  At 4th circle they tell you the cautionary tale of a cleric with a beautiful but unresponsive mistress, whom he touched by Hell's Corruption to try to bring out her dark forbidden desires.  And then it turned out her dark repressed desire was for LOTS OF BABIES obtained by any means necessary, and she was chosen by Pharasma as a cleric.  And -- although the fact is not at all popularized in Cheliax -- Asmodeus and His Church do acknowledge that Asmodeus is in a chain of command with Pharasma, who is mightier than He even if She is so indifferent as to be useless as a tyrant.  The point being, you don't Maledict Pharasmin clerics, or torture them, or even keep them as slaves -- although, again, that fact is not popularized.  You just exile them out of Cheliax, unless they promise to be Lawful or maybe Evil and work with the Church.  So the cleric lost his mistress, because her dark forbidden desire turned out to be not as gloriously Evil as he'd hoped.

Esta did, at one point, lay Hell's Corruption on Mariona, in the desperate hope that there would be anything hiding there to drive Mariona higher in Asmodeus's ranks.

Was Mariona's dark repressed desire to rule the world?  To rule the Church, as Most High?  To rise above Esta and crush him underfoot, beginning a game that Esta would have felt gratified to play, if only Mariona would play it?

No.  Mariona's terrible dark repressed desire was for more medical emergencies to happen around her that she could treat by non-magical medicine, without just throwing a Cure spell at it.

After which Mariona began withholding Cure spells from her troops who'd injured themselves in stupid ways, and treating them nonmagically instead.

This is more or less exactly the sort of thing that seminary warned young Esta would probably happen, if he ever hoped for Hell's Corruption to do anything useful.  It's shaped around being not literally utterly completely useless in combat; meaning it doesn't so much unearth the dark desire that is so tempting as to turn a paladin away from Good, as the dark desire that manages to be very distracting if your mind starts fantasizing about it.

But for Esta to now hear that 'Merrin' was supposedly running around all day long being a 7th-circle-grade non-magical field medic... has a certain familiar ring to it, is the point, here.

Esta has heard of traps and games like this, sprung and played in the First World that the gods made and then abandoned for its flaws and incoherence; games of the Fey, as they are known to laity.

If this were Fey work, the general concept would be to trap Mariona in a prison of her own desires; and there would be a game, perhaps, of Esta being given a chance -- not at all necessarily a fair chance -- to make Mariona see the illusion or reject her supposed heart's desire.

In that version, all Mariona's gear and all her new skills would be -- illusion, or something akin to it, though maybe of a form real enough to bite.  But made out of the substanceless chaos of the First World.

Possibly if the game is being set up by Ŷ̵̘ö̸͙g̷̗̃-̴̖̈́S̵̗̿o̸̹̽t̷̝͝h̵̼͋ó̸̭ẗ̸͖h̵̝̃ it all has a reality of a different order.

(And yes Esta is just thinking the name at this point, because if he tries not to think the name and use euphemisms, it starts coming out as Ṱ̵̌h̴͚̐e̸̩̒ ̶̢̈G̸͚͂ṙ̷͕e̶̿͜á̵̬ţ̷̚ ̸̥̀Ṋ̴̀ò̷̬ő̴̹d̴̺̈́l̴̩͋y̸͚̅ ̸̼͑O̶̯̊n̵̜͠ė̵̹ and such, and that is probably not better.)

It's a hypothesis, and a working theory.  Esta has by now gone through several of those, in this place.  And he is old enough to have lived out parts of his life where he was hurt for jumping to conclusions; and also, of course, hurt for having failed to come up with any theories at all.

He has found no better answer -- nor do the more senior clerics teach it -- but to go on thinking, and be ready to step back from wherever you place your foot.

Esta does pay attention to the actual content of what Merrin is saying.  Reality or game, you have no choice but to play it either way.

And eventually Merrin’s 15-min-warning alarm goes off.

(She did find a timepiece for Estha - she has a couple of tiny reprogrammable simplified-alarm-display-consoles for scenarios where she has to recruit less-injured bystanders to monitor the more injured ones while she rotates between many casualties, and it turns out it’s reprogrammable enough to be willing to display a clock time from another planet’s timekeeping system, though not - at least not at Merrin’s skill level - to display it in a numerical symbols that he can read without magic, he’ll need to learn the Baseline numerals.)

…Is there anything else that seems critical to hit in their planning discussion while Estha still has Baseline vocabulary readily at hand?

Nothing with an obvious dependency on Baseline.

(Estha has asked some hopeful questions about what her technology can or can't do.  Some of them incredibly strange and sounding like, well, like all of Estha's memories of dath ilani technology have been incredibly thoroughly obliviated, as if he were being disoriented and realigned on an alien axis, and not just having sectors deleted.)

If Merrin wants to try for a DC 25 Linguistics check btw, she may notice that Estha's shared [Utopian] seems to have something like a weird conspicuous hole corresponding to the same set of concepts Estha doesn't know.  [Lightning] as in [lightning damage] does not sound like a primitive term; it sounds like, say, hypothetically, a compound word built out of 'electrical', in a language that then had the simpler 'electrical' word ripped out.

Merrin is paying a lot of attention to the bizarre experience of understanding a language she did not actually learn but had inserted into her brain via some sort of mentalistmagic phenomenon, and also it's an annoying and frustrating language that has a ton of specific terms for things irrelevant to her and is missing basic vocabulary for a lot of things that are relevant to her. However, she's not actually a Linguistics genius and she is not going to catch it right now. 

Her overall impression is that her technology has been critical for her own survival, but one thing it absolutely cannot do, unlike - maybe - Estha's [cleric] abilities, is to get them off this planet. She's briefly mulled on the idea of trying to engineer a stronger radio transmitter, in case there's...anyone listening...but it seems very unlikely that this solar system has another habitable-zone planet with intelligent life, and and alien civilization with the capability to rescue her, and also she's not that good at engineering.

Well, yes.  If you want to get around [Creation] and not just one dinky little planet, you had best become a [cleric].

(As opposed to, say, a wizard.  Oh, they get Plane Shift eventually, but only a few of them, and even fewer before they're too old to appreciate it.  Esta doesn't say this part out loud, because it's evident that "dath ilan" lacked all wizards and he doesn't want to call further attention to further divergence.  Excellent taste, though.)

However.  The [Plane Shift] needed to evacuate them requires [tuning forks] that are in his lost [Bag of Holding].

Esta will go through the parts of his [spell loadout] that seem relevant for finding his Bag, or those which he does not definitely know to be irrelevant -- [Magic Mouth], for example.  He will omit, for example, Suggestion.  (Esta is not assuming Asmodeus meant him to use that one on Mariona; its alternative as a domain spell was Dispel Magic and that he might have been even less likely to use.)

He will explain that his methods for protecting the two of them from heat and cold for [1 day] are an [Endure Elements] that he can cast upon her, and that was previously operating on him upon his own arrival; and a much stronger [Extended] [Planetary Adaptation] (4th->5th) that he can only use on himself.

...Esta will say out loud that he is not telling her about all his [spells] because apparently dath ilan culture thinks that Merrin may be really offended and estranged if evidence later arises that Esta can cast a spell he did not disclose, without this stupid fucking disclaimer that Chelish three-year-olds would not need.

If dath ilan is in truth a dreamworld meant to seduce Mariona, Esta (1) thinks this says some unflattering things about Mariona's relationship to social skill checks and (2) totally sees it, frankly.

That does actually make Merrin - who is, in fact, tracking that Estha might not be entirely forthcoming here because LAEIRTHE WON'T SHUT UP ABOUT IT - feel friendlier about the whole interaction! See, Laeirthe, he didn't need to say that! He could have just not said anything! Surely this is some evidence that he's choosing to operate less than maximally adversarially? 

Endure Elements, when described, sounds like exactly the solution to their problem – it's not even something that only acts on a building! Modulo sunburn, they can just go out and do things while they have daylight, even during the dangerously hot hours of the afternoon! 

"What additional protection would [Planetary Adaptation] give you?" she asks him. "Does it help with sunburn? I can wear my suit - if I have Endure Elements it's fine that it can't really keep up with cooling in the afternoons - but the sunlight is a lot more damaging here." 

It's categorical protection from the ordinary environment of the planet, full stop.  If the seas are boiling poisonous acid, you can swim in them and drink from them.  If the air is vaporous poisonous acid, you can breathe it.  If there's no air at all, you can still breathe it.

It's related to 4th-circle [Planar Adaptation].  [Planar Adaptation] will let you survive in the literal [Negative Energy Plane].

This will approximately translate to:

The Doomplane.

It is full of Doom Energy.

Doom Energy is the ontologically simple essence of unhealth.

It can be used to perform a kind of twisted cryorevival, but instead of getting the original person back, you get a Doom Entity.

And yet, this still somehow feels like the 'doom' in 'doompunk'??

Maybe being able to throw Doom Energy around, if you can do so safely and without getting yourself killed like an idiot, is actually pretty cool???*

Anyway.  There were probably some other important things being communicated here besides all that linguistics stuff.

(*)  Esta has successfully convinced himself that Asmodeus is not a god of fucking useless channels.

Merrin is rapidly accumulating ADDITIONAL QUESTIONS about this magic system but probably the Doomplane of Doompunk Doom is not going to be immediately relevant to their two-person-team survival on an exoplanet that does not, she doesn't think, have any Doom Entities or at least that would feel like a really weird and insufficiently earned-with-foreshadowing genre twist in the narrative tropes.

...It does remind her of her mental note about Estha's super doompunk outfit. Which might not be evidence of anything! Dath ilan's cultural associations are not going to be universal! But she is now, increasingly, confident that this is not her Estha. No, she doesn't know how any of that works or what any of that means. Those sounds like questions for smart people, not a simple narrowly-specialized endurance medtech. Merrin is getting...kind of tired...of all the quicksand-reasoning here, and it's kind of impossible to keep track of in the middle of a conversation anyway. But - mental note.

"...So it sounds like you could even swim around in a tidal bore, and be fine?" she says. "And so can I, with the suit." Is it wise to immediately try the incredibly dangerous stupid stunt again? Probably not! But it in fact went fine, she didn't even hit any rocks despite being very distracted and not really optimizing for her own safety, and it'll be strictly easier if she instead has Estha alongside her and equally capable. 

Does that actually help them? She's thinking...

"This idea doesn't work if you do need to [pray for spells] at planetary dawn," she says. "As opposed to roughly 23 hours after you woke me and did the translation [spell], which was at...63:00-ish, I want to say? So 23 hours after that would be about nine hours after dawn. So we'd need to make a call at sunrise, depending what happens then. But - what I'm thinking, is that the next tidal bore is due sometime between fifteen and thirty minutes after sunrise. And if we can both safely jump into it, that's by far the fastest way to get a nice long way upstream. Probably as far as your bag could have gotten. And we can do a lot of searching before your [Planetary Adaptation] wears off. High tide will be 12 hours later. Low tide isn't until 30 hours later but it'll get low enough to expose the upper stretch of tidal flats long before that, and I think it's less likely the bag was swept back out with the outgoing tide and is downstream of us now." 

She makes a face. "...That gets us about 24 hours of searching - and I probably don't even need Endure Elements for it, the water's always cold and my armor can handle heating, but it might be worth it to save battery power, 24 hours straight of hard swimming with full heating on is pushing it."

Pause. "...If it turns out your [spells] aren't renewable ten hours later, then we'd need to be back here before 37:30 when yours wears off, to shelter in here. But if you do get more new spells ten hours later, then we'd have more. And maybe even the one to locate an object? - I think you'd want to time that one for a little after high tide, when the current is just turning and not too fast. We could cover a lot of river in twelve minutes, maybe get close enough to it. If you don't get it then we look the hard way, I guess." 

Glance up at him. "Does that sound potentially workable? ...And can you handle 24 hours straight of searching, I know I can but in dath ilan it's rare." Her Estha couldn't do that. 

"There were several excellent ideas in there.  It hadn't occured to me to use the tidal bore itself as our means of swift movement along the channel, with a [Locate Object] running."

"The difficulty is that if [Planetary Adaptation] is like [Planar Adaptation], it is just that, adaptation, not actually protection.  I would think it would let you breathe acid air and drink acid seas, but not breathe beneath an acid sea; for if you were a native humanoid of that planet you could not do that.  Maybe with clever targeting I could make the [spell] to treat a volcano as the relevant part of the planet to adapt to, and then swim in lava -- but I would not trust my [Spellcraft] to attain that on my first try."

"There is also the point that I was not given [Locate Object].  And yet, if I am truly connected to my [god] and It saw me truly, the [spells] I was [granted], suggest I should be able to solve this problem today, without [praying] again."

"As for the matter of whether I can work at a sustained pace -- you have seen me do it, Merrin.  But in addition to all your memories of our actual profession seeming to have been erased, you would also no longer have the concept of a [Belt] of +4 [Constitution]."

"If I was certain you were still the Merrin I remember, I would have no hesitation about offering to let you try on my [Belt] for a minute to reacquaint yourself with the concept.  As it stands, I must ask you explicitly if you will [swear] to return my [Belt] to me after a minute.  People are sometimes reluctant to give [ability] [enhancement] [items] back, the first time they try one on."

(The word [Belt] conveys that it is a [magic item] filling the [Belt] [slot], rather than any particular sort of clothing, but it does have a connotation of usually going about the waist.)

([Constitution] is an [ability score] that governs over [vitality], [Fortitude] [saves], and of course general healthfulness in the medical sense.)

(Esta has not neglected to notice the point where Merrin is now addressing him as if he were not of the 'dath ilan' that she remembers.  She is of course correct in this, but it still reflects a possible gulf opening wider.  Esta is in fact extremely reluctant to take off his Belt of Constitution, even temporarily and even with his no longer being injured -- but that's exactly what makes it a huge impressive token of trust, that might keep 'Merrin' trusting him as she trusted her Estha.)

There is SO MUCH NEW VOCABULARY! So many new concepts! Merrin kind of desperately wants to be taking notes right now, but also she kind of doesn't want to take notes that Estha can read, and wow she hates that, she is not built for this, she had trouble navigating even the basically friendly socialdeception games of dath ilan (and, yes, her Estha did find it amusing to tease her about this). They have logistical problems and she wants to just solve those together and not have to worry about all of the confusing metaphysics questions about how the larger stranger Reality even works and DEFINITELY not about whether this-Estha is lying to her about everything. 

She doesn't get to have that, does she. 

...The question, then, is whether it's a wise idea to accept his offer of trying on his belt, when he might be lying to her about everything. Also she is MILDLY WEIRDED OUT by his asking her to make an oath about giving it back, as though it's that much in question, though also she just kind of tries to have an instinctive flinch about promising things now. Merrin sure has made some questionable promises in her life without entirely thinking it through! You know, like the time she promised not to leave the room the entire time Kalorm was unconscious! 

"- I'd like a moment to think about what I'm comfortable swearing," she says, so she's not just awkwardly going quiet on him for unclear reasons. 

Kalorm unsurprisingly thinks this is a pretty great Merrin-trait but, yeah, maybe awkward when uncool people are involved. 

...Laeirthe is approving of Merrin flagging it and trying to run an appropriate level of paranoia, but - is not sure what the specific threat model would be here? Merrin does not seem like someone who will even have trouble doing a thing she doesn't emotionally-want to do because she committed to it, so the failure mode would be, what, proposing that the [belt] does mind control to her? But in the world where that was true and also this request specifically is a case of 'Estha' operating adversarially, then - what's his plan for how asking her to swear an oath that she then won't be able to keep would help with his goals at all? 

And there are perfectly sensible reasons for him to ask it of her. It's a key part of his own gear, obviously he's motivated to hold onto it, and - he's probably operating with just as much uncertainty and paranoia around Merrin's traits compared to the other version of her who he apparently knows. 

In summary: sure, maybe it's some kind of trick, the fact that Laeirthe can't see an obvious specific threat model does not guarantee there isn't one. But there's also information value to accepting the offer.