The old saying 'why trust what you can verify' out of dath ilan seems to apply with some small degree of additional force when one wrong thought not even inside his own mind potentially destroys the multiverse when it could otherwise be saved.  So he is, in fact, going to be doing some extra checking and reminding here.

She does not, actually, mind. Keltham trying to make sure they don't accidentally blow up the world is the most sympathetic remaining thing about him. ...that and his smile when he succeeds at casting a complicated spell.

After some recovery time with only Splendour boosted, he tries getting a Fox's Cunning, which takes him to +4/+0/+6 (over baseline 18/16/14, innate +3/+4/+5).

When nothing bad seems to happen to him after a few minutes, he applies an Eagle's Splendour to himself, and takes off the +6 Splendour headband, which takes his stats to 25/20/23.

It... does not appear to send him back to the way he was before... his emotions weaken but do not vanish...

So he puts on the +4/+0/+4 headband, before the spells run out, to stabilize his stats at 25/20/23.

You can't really get much done with only INT 21, is the problem.  He doesn't know, in retrospect, how dath ilani who are only +2sd Intelligence get through life.  He sure didn't get far on +0.8sd... well, probably it's that nearly all dath ilani never try to do anything really complicated.  Or if they do, they take a lot more time to do it.

And he goes back to work, or tries to.  He is still, tired, inside.  The lack of a concrete deadline on how long he needs to keep this up, is not helping.  Especially at only Splendour 14+5+4, which, he suspects, does not end up the same thing to a dath ilani, as Splendour 14+5+4 is supposed to be to most Golarion natives.

But INT 25 is enough for him to go back to his MSOM (Magical Simulation of Magic) crafting attempt.

He's gathered, by now, that Baseline is not the key to wording Wishes, that there is something that takes language and goes from there to a spellpattern and that is why Wish phrasings matter so much.  When he gets to INT 29 he will cast Arcane Sight and Haste and watch his other stats getting Wished-up by efreeti, possibly get efreeti to cast some other standard Wishes just to watch those, and maybe at INT 29 he'll be able to make a standing leap to some understanding of how Wishes turn into spellforms.  Hand-building an emulator of magical physics, or even trying and failing to do that, seems like it is plausibly on the critical path towards his being able to do that later, if anything is.

Building his Magical Simulation of Magic would probably be any degree easier if he had Carissa Sevar's kind of Spellcraft.  But not that much easier, to be honest.  He's got his own Armillary Amulet now.  Most of the challenge, fundamentally, is coming up with any system of magical physics with a visible subsystem that emulates an isomorphism of magical physics.  Not making the process happen, coming up with any process with that property.  Crafting ad-hoc supports for holding the systems together...

Well, he could, in fact, go a lot faster between trials and errors, if he was better at crafting spellsilver into magical supports and then tweaking the crafts.  But the item-crafter he has on hand, in his base, is somebody to whom it takes longer to explain what he's trying to accomplish, each time and tweak, than it does for him to try the tweaks himself.  At least this way he's learning himself, at INT 25, and speeding up at the exact form of crafting he needs to do.

...he gets another Eagle's Splendour and swaps to his +6 Intelligence headband, and, yeah, with stats of 27/20/23 it feels like he is able to make real progress on a couple of his current challenges, for the few minutes it takes before the Splendour is about to run out, and he has to put his +4/+0/+4 headband back on.

Changing abilitystats, he suspects, is not actually good for him.

Not as bad as swapping Wisdom up and down, forming new mental skills and circuits that depend on a certain kind of boosted reflectivity which then abruptly vanishes just as his brain was getting used to it.  Bumping Wisdom up and down is probably literally the worst idea.  (The worst idea inside the realm of practical abilitystat manipulation, to be clear, not the worst idea in full generality.)

But even Intelligence going back and forth between 27 and 25 is maybe not as good for a dath ilani brain as he would have liked, in an ideal world.

It's time for a conversation that he's really dreading, and if he was significantly less calculating, or less reflective, or had less force of personality, he wouldn't be able to bring himself to say it.

He is going to try to explain that he thinks all the changes of abilitystats are really not good for him, and then, ask Carissa for her headband... more or less for the foreseeable future.  She can have all of his own augmentation items, they can spend even more money on Wisdoms and Splendours, but - if the time she's bought is going to mean anything, and if - it's considered a good thing that he holds himself together - he needs a constant statblock, and he needs that statblock to have INT 27.  There's not, really, any other obvious way to achieve that, unless he's missing something.  It's not even - obvious - that it would be an especially good idea for him to take off the headband - her headband, Carissa's headband, for which she sold her soul - while he is sleeping.

...he'd tell him to get lost, but Carissa has surprised him before; she is stronger than he.

"How's it going."

He will lay out the situation: he needs INT 27 not INT 25, he could probably benefit from more Wisdom but bouncing Wisdom up and down is likely to be bad for his brain, dropping to Splendour 19 isn't likely to be good for him either, bouncing abilitystats up and down in general seems plausibly to have not been good for him.  Possibly very not good for him.

Here are some expected utility calculations his INT 25 self tried to do from the Carissa / Pharasma point of view, double-checked for a few minutes of INT 27, though this is more of a Wisdom-laden task and he has not dared to augment Wisdom yet.  The primary point is that he can in fact get to INT 27 using his +6 Intelligence headband, and get work done that way, and would have to do that, and would do that, to get the basic capabilities he needs.  He would just, probably, damage his emotional and mental stability in the course of doing that.

He will keep his voice very dispassionate and his face expressionless, as best as Splendour 23 can boost a dath ilani doing that.  Showing any emotions to Carissa would be emotion-bombing her, under the circumstances.  The underlying extent to which he is holding his sanity hostage against her, even as not technically a threat, is horrible enough already.

"You want the headband."

For the foreseeable future, which is now less foreseeable after extending their intended work time.

He has a complete set of individually +6 headbands, a +4/+0/+4 headband, a +2/+2/+2 headband, he can pour any non-project-torpedoing or non-hand-tipping amount of resources into acquiring more scrolls of Owl's Wisdom or Eagle's Splendour, Carissa Sevar is not as restricted as himself if she wants to try renting the Pharaoh's +4/+4/+4 or finding somewhere to buy a +6/+6.

"Okay, some considerations. One, I want to show up and encourage my cults in Vudra and in the Kelesh Empire and in various other places, I suspect it improves the odds of Pharasma working with you or the odds I don't get squished mid-ascension or something in the genre. I think I need to be wearing the headband for that for maximum credibility. I could conceivably do that right now and give it to you later today after 20 hours of cult-cultivating, or I could conceivably do it while you sleep if you're all right with me having it while you sleep, but it'll be bad, I think, if I don't get to do it at all.

Two. I do think things will go better if you're smarter. I also think they'll go better if I'm smarter and separately from benefits of me being smarter I think they'll go better if I, uh, am someone you respect and listen to? And I think we're kind of already on the fringe on that front and if you're notably lots smarter than me you won't in fact listen to me at all, and I'm scared that'll make things overall go worse. 

I'd agree in a heartbeat if you'd agree not to go ahead with the overall plan without my say-so - not expecting you to agree to that, just, trying to figure out sufficient conditions and might as well name the obvious one. 

I think I'd agree if you agreed to - let some worlds live that seemed not quite worth it to you but close enough you weren't sure, some marginal ones - I don't know what agreeing to that would look like -

- and, uh, most of what I'm using Wisdom for is not getting really mad at you every time you open your mouth so if you were able to do that on your end maybe I could just do the headband of intelligence and it'd be fine, but I know it's hard on you when you feel like you're the only one reaching across the divide, and I really wouldn't be able to do much of that, without the Wisdom headband, it's hard even wearing it."

"I could do the marginal thing.  Don't expect to run into many marginal cases, but - if I do - sure."

"It's funny how, now and then, and despite a lot of things, I get the feeling that you are in some deep sense a better person than I am.  I mean, Carmin probably wouldn't even think it was funny, she'd just say, sure, Carissa would have grown up to be a much better person than you, given better circumstances, and now that's starting to shine through."

"I - would not be very surprised if a good solution here, ends up looking like, my staying mostly out of your way, for the next ten days subjective, pending a trip to the City of Brass where you get your baseline Wisdom wished up.  After that point we'll both be INT 29 and it will be quite a subversion of my expectations if we - end up talking to each other the same way, after that."

"I don't trust my brain to be okay while I sleep, if transient scaffolding for my cognitive reflectivity gets erased while I'm doing that.  Let's frontload the Vudra and Kelesh visits."

"Do you expect to be okay with 6 points of sudden Wisdom loss?  I can try to locate a +4/+4/+0 artifact headband on an emergency basis while you're touring the local meetups of your fan club, but you'd be at less than max Intelligence so I don't even know if you would."

"I think I'd rather have Intelligence. Wizards usually go much harder on Intelligence and it works fine so long as you can also be kind of an emotionally insensitive jerk, and you generally can, if you're a powerful wizard.

I'm not - trying to be Good, here, I'm just trying to survive. I'm just in a weird situation where they're the same thing."

"I'll let Carmin be the one to call bullshit on that.  You'll probably believe it more coming from her."

"Okay. I'm going to go do cult cultivation, then. ....I'm going to burn something like 50,000gp in scrolls on looking cool and you are not allowed to complain about this at all."

"Wasn't even slightly considering it.  Off with you, you need to talk to some of the people correctly relying on you for salvation, non-Good person."

(Notably missing from Carissa's compact with him: a specification saying that, if he does release Rovagug, Carissa shall not at this time be prevented from escaping to Elysium or the Maelstrom.  Both of those planes are supposedly infinite, and the Maelstrom in particular is supposed to ultimately head off into the chaos outside Pharasma's bubble; which would make it much more likely that you could escape Rovagug, starting from there.)

(He's not suggesting this clause, if she hasn't thought of it; because Carissa might, at that point, demand that clause in order to not fight it out with her own self-image, which clause would then potentially hamper her actually saving the multiverse and also force her to think of herself as a worse person.  It's just funny because, Carissa's real emotional priorities being what they actually are, she hasn't thought of it.)

Well, you can't risk the entire multiverse for the sake of being more likely to survive its destruction!! If she were literally any of the other trillions of people in the multiverse she'd be so mad at herself for even contemplating that trade! 

...anyway. Teleport and Fool's Teleport and Dimension Door and Damnation Stride and Firefall and lots of Vision of Hell prepared, check.

Scrolls to cast: Telepathy, Overland Flight, Spell Resistance, Programmed Image, Cloak of Winds, Getaway, Life Bubble, Contingent Teleport, Mage Armor, Spell Immunity, Greater Spell Immunity,  check. 

Some of these are necessary for her plans, some just sounded like fun and when is she going to get the chance to use the most bizarre spells Keltham's shoppers could find anywhere on the planet, if not now?

"Is there anyone here who's been to Vudra - I guess whoever did all this shopping must have gone -"

That would be him.  Keltham has made his services, hired on a monthly basis, available for this little trip.

Great. Does he happen to know anything about her cult in Vudra? She's happy to just be taken to a major city but if he knows where to start they can do that.

He has not particularly been looking into that, no.  Among many other reasons not to, it's suspected by Keltham of being a Cayden intervention and therefore nobody is to talk to him about it.

"Fine, where's your Teleport to."

"I can do Indapatta, the capital.  Niswan in Jalmeray.   Sumadhadra, the most important port city for their trade with Tian Xia.  Those seem the most promising places to find your cult.  I could also, for example, teleport you to the undead-haunted Palace of Ivory and Bone, but I do not imagine that you are interested in such more exotic destinations, on this trip."

"Let's do Indapatta. I think the undead are probably an unreceptive audience for pitches about how if you help me conquer the world you'll have eternal glory in Hell."