Seeming to be given everything, and finding the courage to trust in it, and having it all ripped away from him, has wounded him on a level that - doesn't really seem worthwhile to try to recover from inside of Creation.
If he could live happily ever after with Carissa, though, he would give it a try, for that.
Losing her is - not all of the hurt - but it's most of the lasting wound that feels like it couldn't heal naturally and isn't correct to heal artificially.
He is glad to know, at least, that she loves him, and misses him; and he loves her, and misses her, and he also wishes he was doing anything that wasn't this. She wouldn't have very much forgiveness to earn, for what she did under threat of Hell. Peranza and Asmodia getting shattered might have been a problem, but they weren't, and -
- he doesn't want this doomed course. He just doesn't think that even the gods and the eroLARP are on course to get them out of it. On the surface of things, the story they're inside has too many dangling plot threads and character arcs cut short, for this to be a perfect run that gets the best ending. And he hopes that this was just a dry run, a possibility almost entirely not real that gives valuable information to Nethys or Cayden Cailean, but he knows that his awareness of his own awareness is probabilistic evidence against that.
Carissa doubts this is the best ending for Nethys or Cayden Cailean, but she doesn't care at all about either of them and remains the slightest bit optimistic it might be a very good result for her. ...for Keltham seems less likely, but maybe she'll think of something.
(He is a little jarred by the thought, that things could go well for Carissa but not him, he had intuitively modeled them as - closer-linked in fates, or as people, than that - but he sets the thought aside. There is a known clock-bound on all of this.)
They don't have that much time left on Detect Thoughts. There is an Algorithm to be shown her. Before then he'd know her informal thoughts, on promises and oaths with the lover who left her bereft so he could destroy Creation and diminish the reality of all the souls inside it; maybe for reasons based on unshareable evidence, reasons that she will end up sure herself are mistaken.
She is going to be a Lawful god. There are a lot of things, important things, that you can only build that way. And Nethys sees other worlds, sees other Carissae, sees other Kelthams, and she is pretty sure she gets more of what she wants, in the grand view, if her word is meaningful, if it's possible for her to mean what she says. She is not sure if she wishes she'd sold Keltham out to whoever would listen the instant she realized his plan. It depends what the gods have in store. But she didn't, and won't, even if he is obviously wrong, or obviously monstrous; if she were different, she wouldn't be here.
Lawfulness is Pharasma's take on things. It's a bundle of ideas that Pharasma chose and bundled. It is the sort of package-deal that people maybe see through at this INT/WIS even if they have no training at all in seeing through package-deals; and Carissa now has some of that training even if it is secondhand off dath ilan. It would not surprise him terribly if somewhere in this plot they come to a point where Carissa somehow learns that she's beyond the sight of Nethys. He doesn't predict it very strongly, but they are inside of something with at least some storylike qualities. Any pillar of her trustworthiness that she names to herself, knows to herself, as her own support, is liable perhaps to be tested.
Set aside Pharasma's bundle. Set aside Nethys's manipulations. If there were no Pharasma and no Nethys, who would Carissa be, and why?
Carissa is not, actually, sure that you can neatly set everything aside like that. It's not that she agrees with Pharasma about everything, it's not that she wouldn't kill Nethys if the opportunity presented itself and wouldn't destroy any universes. But there's no truth of who and what she is that is totally separate from the world in which she operates, has always operated, will always operate.
In a world where it was impossible for gods to credibly communicate facts about their intentions to other gods, and impossible for mortals to do it either even at lower resolution; there might still be some algorithm in dath ilan. But it wouldn't be a description of how things work, and Carissa would not let universes die for it.
She lives in a world where you can choose whether anyone can trust you, or not, and it is in that world and in that context, and in the shape of the god she wants to be, that having given her word she won't kill Keltham even to save the world.
Look, it's not that improbable that Carissa's going to end up in a different universe at some point, maybe one where in fact there's not a Pharasma and a Nethys around. In his personal experience, only 50% of universes have Pharasmas and Nethysi in them, and 100% of his direct samples have ended up in another universe at least once...
That was a thought-continuation out of dath ilan, a reflex for pressing on thought experiments. But even reflecting more carefully on where his thoughts were steering, this doesn't seem like a thought-line to abandon. "Because of Pharasma and Nethys" feel like weak contingent reasons to him, a reliance on something outside of Carissa for her strength and trustworthiness. He's got a family of Starstone speculations where Carissa's degree of understanding and self-understanding about this topic may affect how Lawful of a god she ends up becoming, maybe even her power as a Lawful deity.
From his perspective, the existence of Pharasma, or spells that detect "Lawfulness", or afterlives that depend on "Lawfulness", or alternate-possibility-perceiving gods like Nethys straight out of contrived-thought-experiments, are a kind of external crutch. He feels about them the way that the Irorian monk, Derrina, seemed to feel about the Crown of Infernal Majesty. Seizing advantage of them is one thing; being unable to operate without them is another.
When you become a god, you decide what kind of being you are, in an important sense; gods don't change very much. You can't, exactly, become Abadar and then decide later that you're going to cheat someone just once. Someone who'd cheat just once would never have been Abadar.
The thing humans are doing is weaker, and worse, and most of the justifications they'd give for it are contingent and complicated -- not just the ones labelled 'Law' and 'Nethys', but also the ones labelled 'honor' and 'dignity' and whatever else. Probably most humans wouldn't, actually, keep their word if it might mean the world was destroyed, not humans who really understood how unimaginably horrendous the destruction of the world was, and that fact probably limited how many humans could be steered through whatever contrivances have steered them to here and now.
It is a fact about Carissa, that she has meant it, every time she gave her word, even this time when she gave it believing that Keltham was the most profound evil the world had ever known, believing him much much worse than Asmodeus, hating him. It is also a fact about Carissa that, mostly, this habit was not built out of the pieces that gods have as pieces of themselves, the parts of them that make them able to commit to things. It was built out of the knowledge that devils do it, and the desire to be one, and out of the desperate hope she could talk Keltham out of this, if only he could trust her enough to let her try.
If he wants to know if she understands what pieces are in gods that let them commit to things - yes, she understands those pieces, and intends to build herself around them. If he's looking for a different historical-origin-of-what-Carissa-is, he won't find it.
In his own causal-origins, he grew up with a deep respect for those honorable things people do which are not founded from their first beginning on exactly correct decision theory, but which they can nonetheless feel deeply within themselves. He's not objecting to Carissa's causal-origins, not at all.
The main point where respecting imperfect decision theory blows up on you is when not both sides are respecting it. It's often emphasized in dath ilani fiction that you may not be able to get away with negotiating with aliens this way; that if you try to blunder ahead on just honor, the aliens may look at you and shrug and say, "Well, that thing sure is effectively a rock with Cooperate written on it, rather than something whose output logically depends on our own output. It's imagining us as acting with honor, and that's false, we've got this other thing instead. So what do we care about how this thing conditioned its behavior on the behavior of this imaginary alien in its mind? It would have imagined the same alien no matter what we do now." This is obviously-in-retrospect a concealed warning against honorably trusting to the honor of computer-based intelligences who don't share that evolutionary history; but it also points to a potential failure of the join between two mortals, at the point where they both become gods.
Abadar will bargain fairly with you even if you don't imagine Him exactly right. It's in His utility function, and not in a weird alien way where He'll maximize you into a weird side corner of possibility-space in course of maximizing how fair He was to you. Abadar is actually about fair dealing, not exactly in the way that mortals see fairness, but in a way that makes mortals be actually safe to bargain with Him.
To reciprocate the trust that underlies mutual Cooperation in the Prisoner's Dilemma - even of something that imagined you wrongly, whose output doesn't quite logically depend on your own output - is yet still within the utility function of someone once called Keltham, who once was Abadar's priest. At least, it's stayed in him this far, though he's never, quite, really cared enough about any event in this possibly-unreal universe for that pillar of himself to be tested; it's not as if Carissa was being twisted/torn/shattered in Hell at any point during this, it's not as if he was given a chance to undo his children by lying.
He is not sure it is quite in Carissa's utility function the same way, that even with Creation at stake She would never betray a tiny mortal who trusted in an incorrect imagination of Her - or would She not? He does not know and therefore asks. There are other courses between them, if the answer is 'no'; this is not a question where only one answer preserves cooperation between them. (And that there are other ways, he wouldn't ever lie about to her in order to get a more honest answer from her, even if his thoughts could be that concealed.)
She knows he wouldn't. She's grateful that he wouldn't. It's why she's here, instead of selling her information on what he was going to do to Osirion for a lot of money and then warning all the gods.
She thinks that Carissa is, actually, Lawful Evil not Lawful Neutral; she might betray a tiny mortal who trusted in an incorrect imagination of her, whose trust in her bore no resemblance to the bright clear thing that devils and gods do. She'd try not to; it seems unlikely she would ever have to, and she wouldn't find it funny. She'd advertise as fact that she might do it, and she wouldn't do it if she'd said she wouldn't.
But if there were a tiny mortal who wanted to destroy the world, and who sought lightning in the sky as proof of her commitment of confidentiality, and there was unrelated lightning in the sky and the mortal warned her -
- she'd prevent the end of the world.
Yeah, he kinda figured.
To him it seems an obvious attempt at resolving this, that while they are in this place halfway between mortal and god, while their causal-origin emotions are still in them and the respect of it, and also they can understand and use real decision theory, that they build the real structure of a logical correlation between them, based on reading each other's minds and constructing real models of the decisions that they'll make over and over to not betray each other.
He understands that something else might rise up inside her, once her own mind is no longer being read. But it will be something that knows decision theory, that knows that he was modeling how she might think even in that moment.
By the nature of a bargain like that, the later Carissa-become-goddess could only be bound if She believed (presumably accurately because goddess) that She really wouldn't have gotten a chance to save the world, if She'd made a different logical decision in the physical places it's multiply represented, in the future at Her later time of action, in the past within his accurate though necessarily abstract model of Her.
This in turn means that he has to be ready, now, to remove that future capacity from future-Carissa, if he makes a different prediction about Her.
...he hopes she is not incredibly upset about this. He wouldn't have to walk through it that way if her utility function said to be trustworthy even to things that haven't sufficiently accurately modeled Her own future decision to have introduced a logical counterfactual dependency on Her within the past (not just that the past happens to correctly guess Her decision, but that the past would have made a different guess if future-Her chose differently). No statueing nor any other deprivation of consciousness will be involved no matter what.
She's not upset about that. She's harder to upset now anyways, but even the Carissa he first met wouldn't have been upset about that; using force to get what you want is not an upsetting move, not the kind of thing that stands in the way of further cooperation, as long as you're provoked to it predictably.
Some part of him is still surprised by hearing that, strangely. At this level of cognition he'd better only need to be surprised once, or he's asking for a refund on Golarion's whole concept of intelligence enhancement.
Let them go to it, then.