Going direct for oral, hm?  Keltham doesn't mind.  There's a family of sex jokes whose punchlines go, "Even the far-from-optimal instances of particular-sex-act tend to be improvements-far-above-par" and oral sex is often named as a classic example.

Keltham is already quite worked up, even after taking into account the temporarily distracting part where the sex got complicated enough that he had to start considering multiple hypotheses, so it shouldn't take long to reach the part where he sees whether or not he can surprise Carissa with his other dath ilani sex technique that doesn't require technology but still probably shouldn't exist in a pretechnological world.

He'll entertain himself, and arouse himself further, by trying to hurt Carissa while she works.  Can his fingernails reach her nipples from here, given her current position?

Yes; she can't exactly do 'giggly' while she's working but she can shift her weight to give him better access, see, look, as cooperative as you can get. ('as cooperative as you can get' is ....not actually her preferred kind of Carissa to be? it's weird she even noticed that when she should be thinking about work, clearly something about Keltham throws her off her game which is not a problem she can really afford to have. Cooperative is a perfect Carissa to be, Asmodeus notices people not just for their capacity to rise in Hell but for their capacity to serve Him, wholeheartedly and uncomplicatedly, and it feels obvious that she'd want to do that, so why not reach for that, now, in the presence of the person her god has spoken of as her teacher, why not take the sort of topsy-tervy mental motion after which she feels so small in his presence that to be as cooperative as he could possibly desire is all she can aspire to -

- right. Because she's lying to him, that's the reason not to do that. Because what she wants here is the performance of perfect submission accompanied by the mental state of coldly contemplated manipulation and so obviously it's not going to feel like surrender, it's going to feel like walking a tightrope with a dick in her mouth, of course that'd take a bit of getting used to -)

She squirms about being pinched, and bats her eyes at Keltham.

Keltham isn't trying to read her in very much detail - it's not like he even knows how to read 'level of pain', either 0 or a very very tiny number of people in Civilization would ever get any training on that - actually it's almost certainly 0 because never mind who needs to know*, who would do the experiments to figure that out - anyways Keltham isn't trying to read her in very much detail, just enjoying himself.

He makes no effort to hold back his own rising pleasure, and he certainly isn't going to conceal his tells, as he approaches the arousal level for potential orgasm; he's curious about whether Carissa can read him, and what she does about that if he can.  It would be an observational misstep to tell her what to do, or even hint to her about what to do, before he's had any chance to observe what she does on her own.

(*)  Medical personnel, in fact.

Carissa is pretty sure that she is supposed to get him off, because that is how sex works. It's one of the least complicated forms of human interaction, really.

She's just going to make him come? - Keltham thinks as he reaches the verge of orgasm without any obvious attempts by her to delay it.  That's a bit surprising - maybe there's magic here for restoring male ejaculative potential as a special case of healing?  Or maybe she can't read him any more than he can read her.

Keltham was hooked up to some complicated biofeedback machines, which another society might even have deemed embarrassing, in order to learn this next part; which is why he's guessing that the natives here won't have it.

Even so he has to shut his eyes and concentrate, as he clenches some muscles and relaxes others, and comes just a little into Carissa's mouth.

(That part where men come once, and then their pleasure-experiencing capabilities are reduced for a while, maybe even finished for the duration?

Less than ideal.

Civilization spent money on improving over that until they could no longer figure out how to usefully spend any more money.)

"Surprise," Keltham says, the first words he's spoken in a while.

Carissa has no idea what just happened but probably she's supposed to be impressed? She doesn't have to have any idea what just happened to guess that 'impressed' is better for the mood than 'confused'. 

She sits up and raises her eyebrows and looks at him. Going for impressed, not confused.

"Partial ejaculation technique, learned via machines that give us feedback and guide us along non-obvious intermediates to learning it," Keltham says.  "That's the way we do it without magic.  Do you have a magical solution for the problem where if men have full orgasms they go soft for a while?  Because I wouldn't mind trying that too, if it's on tap."

"Second-circle cleric spell, or there's a potion if you're pretty sure your god only gave you useful-to-the-Project spells today." Paladins reportedly get it at first circle but none of them have ever let Carissa observe this firsthand, because, paladins.

"Used up all my second-circles for the day, and even if my god extrapolated our date he would also know I didn't really need that spell."

"So do you have that potion on hand, or were you just going to let me empty my full reserve into your mouth and then have nothing to do but service you for a while until I got hard again?  Because that seems a little naughty."

Was she supposed to do something different? "Would I do that?" she says innocently. "Be difficult with you, without saying in advance it was Complicated Romance, like I'm from a civilization of savages? We can call for the potion, but I haven't got it in my ear."

He shall delay for later the question of how potions are usually stored in ears.  "Well, back to work with you, then," Keltham says and pulls her head back down.  "Dequote unless you actually did that because you needed a break from oral," he adds.

- that is the most baffling thing that anyone has ever said to Carissa in her entire life. She will simply ignore it.

The night is young.  Maybe dath ilan can still top it.

The next time Keltham gets close to an orgasm, he pulls her head back.  By the hair.

"I was getting close to a potential-orgasm there," Keltham says.  "Now, in dath ilan, a slightly skilled partner, not a professional, just someone who'd put some time and money into improving the pleasures she had to trade, would have machine-assisted training for reading how close I am to orgasm.  If she wasn't relatively skilled, I'd have to expend the distracting effort to say verbal numbers from zero to twelve, to tell her how close I was to coming, so she could slow down or speed up to keep me at around nine or ten, without going to twelve."

"So are you slightly skilled by the standards of dath ilan, Carissa Sevar?"

(Said in what would be, in dath ilan, a naughty male voice, but not at all a submissive one.)

Well, she's hardly going to say 'no', even if she has mostly only used the relevant skillset to not herself be taken by surprise; a guy can pull out, if he wants to do that.  She raises her eyebrows at Keltham again.

"Oh, is that not a game they play in Golarion?  Keeping people in as much pleasure as you can safely give them, without sending them over to where it bursts and stops?"  And do they have any other sex games to replace that one, or has Golarion just not optimized over sex at all, for all that Carissa was talking a good game before - no, sad thought, no sad thoughts until tomorrow.  "If you've never tried that game before, I admit I'm curious to see the baseline of how well you do without any training.  It's not like you could make me come all the way, if I decided not to."

(Keltham can feel that he's not quite doing this right, the naughty challenge that he's giving her; the dialogue he's emitting feels wrong, like he should be - more sadistic in his words, not just his fingers.  There's something deeper and more forceful in him, that wants to speak, but doesn't know how to express itself.  Maybe now was when he was supposed to use Eagle's Splendour?  But whatever this impulse is, he'll analyze it and reflectionize it later.  In sex of all places, you've got to be okay with things not being perfect the first time.)

Carissa vaguely suspects that you can't solve sex in the same way you can't solve sword fighting, the best tactics depend too much on the adversary's tactics. Obviously some people are much better than others at swordfighting, and at sex, but it's not something like logic where there's a correct answer with properties no other answer has; people have incredible sex with succubi or whatever but they don't all describe the sex being incredible in the same way, the way that fleshshaping is in fact mostly described in the same way.  If she tries to think back on all of the best sex she's ever had it has notably little to do with technique, rather than 'I just wanted it really badly that day' or 'I'd never tried that before and that was a perfect way for it to go for the first time'.

...this seems like not the time to argue this point. Plausibly there is no good time to argue that point but right now is a very bad time. "Soldiers don't play that game much," she says. "Not none, though. I would bet I could keep up." The problem, as described, doesn't sound that impossible, even if in Golarion a guy will normally just tell you to slow down or whatever. ...probably if having sex with Keltham is an important ingredient of a plan to seduce him to Lawful Evil, then she can justify the expense of having someone mindread him and telepathically give her cues - and probably she is overthinking this and can just imagine he is saying 'slow down' at the point where she'd expect a guy to say that, and see if that suffices, and involve expensive and risky intimate surveillance arrangements only if that fails. Yeah. There's a good plan.

Dath ilan has no colloquialism for 'I bet' meaning 'I believe'.  Those words can mean only one thing:

Betting.

"Oh, and what are we betting, then?"

“I have been established to intend to win your shirt. I don’t know what you want of me that you don’t already have.”

"In the cuddleroom, one typically bets asymmetrical sexual services one desires.  One unreciprocated oral service not to exceed a third-hour, callable on demand when you're otherwise in cuddleable state, would be a standard thing for you to bet against me.  What manner of sexual service would you demand I bet in return?  My shirt is one of the only mementos I have of home, fitted to my body alone, and also it is a legacy of alien technology far beyond your own civilization.  Even if you bet an entire lifetime of unreciprocated oral it wouldn't be enough for my shirt."  Like seriously.

Literally everything in that category he could possibly name he has already because, in descending order of how obvious this should be to him, he is from another planet and is in wildly high demand for reasons that have nothing to do with how often he goes down on people, he has a dozen suitors even in this highly secure facility and can therefore expect to get away with being as selfish as he likes with at least three or four of them and since all of them know that none are going to object, and also obviously any girl who is difficult with Keltham is getting removed from the project and presumably at that point killed.

“So I could name terms along those lines,” she says, “but I feel obliged to note that a symmetrical bet like that seems very dath ilani, very Neutral, not even a little bit Evil. …and relatedly that it does not sound like you named anything that you really desperately want.”

What??!?  Bets are supposed to be fair because that's what makes them say anything meaningful about the bettors' probabilities!