"I am not sure there is a soul alive of higher value to Hell, and if there is, it is the mortal I am in the middle of delivering to Asmodeus and who wants the option on my soul, which, if he exercises it, will bring him to Our Lord.

I propose an equal split of the gains from this trade, and will reject lesser splits with a probability corresponding to how disproportionately they reserve the gains for you, such that you can't actually do better by pretending to underrate me, but we'll still work something out with high probability if we honestly disagree, paid in Wishes and spellsilver above and beyond the ordinary payment of permanent Arcane Sight. ...and permanent Tongues."

...first of all, mortals aren't supposed to know about any of that, however garbled and incomplete it sounds, and second, if they stumble over a piece of it, you're supposed to shut them down hard and refuse to bargain for their soul and ideally let them get executed by Cheliax.

Carissa Sevar will not be executed if he refuses her; so much seems obvious from the lack of others present to watch her, saving one Priestess who is looking more at him than at her.

But if he's reading Carissa Sevar right, she doesn't know.  Or she doesn't know numbers.

They wouldn't have summoned him to negotiate if they had even a beginning guess at Carissa Sevar's worth; he's not a Count of Hell.

"That is not the way of Hell," he rumbles.  "Asmodeus is not Abadar, little mortal, no matter what company you have been keeping of late.  You can try to hold what secrets you like, and Hell will keep its own, and whoever is closer to Asmodeus in wit and ways is the one to win the compact.  Name to me the price you seek for yourself."

Of course. 

She's tempted to say 'there has to be some devil that will accept that the price of bargaining with me includes this; get me that one'. But there doesn't have to be any such devil. To be a devil is to be perfected, at least along that angle, and apparently perfected in Lawful Evil you don't have any interest in that. Like how Contessa Lrilatha hates Keltham's good faith clause.

But she wasn't refused outright, despite offering something objectively worth much less than a normal contract. 

"Then," she says, "speaking informally to establish the terms for a contract not yet written, for three Wishes, and ten pounds of spellsilver, and permanent Arcane Sight and permanent Tongues, I offer my soul, subject to the option for a mortal to claim it which was previously discussed."

Glosialabolas thinks the equivalent of "Heck yes, fucking score" in Infernal.  It's a large chunk of her (current) likely fair price, but nowhere close to all of it.  And while he can't deliver three Wishes, he can sell his choice of which devil he'll bring back to compact with Carissa Sevar.

"Hmpfh.  I would have to bring forth a superior devil to make such a bargain, if they proved willing to make it at all, at some trouble to myself for one not receiving your soul in the end.  Nor has it been made known to Dis whether you are this day permitted to sell your soul, and the question might need to be referred far up the hierarchy, which is no trivial hazard of time and pride for myself to undergo."

"This mortal claim.  Say more of it."

He didn't just turn her down.  Carissa Sevar asked for three Wishes and the contract devil did not laugh.

Maybe all that talk about 'Chosen of Asmodeus' was not so much flattery as Jacint thought.

She is having the same realization. Maybe she should've asked for more, but. What does Hell believe, such that they'd even contemplate -

"Hell keeps its secrets, and I'll keep mine. The option should grant the mortal the real right to, at any time, exercise the option and make my soul his own, his right acknowledged by all of Hell the same as the right of any great contract devil to the souls they have contracted for and purchased. It is acceptable for the exercise to involve the payment of some fixed compensation to the soul's previous owner. No commitments need be made about the soul's state, beyond that it'll be extant, and its owner while the option has not been exercised will not compact to destroy it."

Is she sneaking that last bit in out of self-interest rather than because Keltham would even think to specify it, yes she is, though she's not entirely conscious of this even as she does it.

A fixed compensation!  The prices are still fluctuating in the markets of Dis, and even demanding thrice the original payment would not suffice to protect the asset if it increases still further.

But that, he can hardly say to Carissa Sevar; some other excuse must be found to reject the term.

"The mortal is not here, party to this contract though you seemingly intend him to be.  Are you hiding things from him, I wonder?  And if so, I wonder, do you wish him to see a compact plainly mentioning some exercise price substantially greater than three Wishes and ten pounds of spellsilver?  For we are not in the habit of reselling at no gain."

He can't just suggest a term about market prices though, or a price reflecting lost gains to the devil who must sell; that will make it too obvious what's really going on.

"The exercise price should be denominated in Chelish currency, so he doesn't get distracted trying to figure out where he can get Wishes. The amount won't give him pause."

"Hoh?  Even if we demand from him what is denominated as ten million gold in the true wealth of Cheliax?  He is so naive?"

"It doesn't serve Asmodeus for the price to be so high he can't exercise it and turn Evil, so I can't let you peg it at that. Five hundred thousand would cover the Wishes and the spellsilver and a generous profit, and there are considerable benefits from having owned me even for a time, if I spend any of it dead so you can learn them."

"Not the way of Hell bargaining for a soul, Carissa Sevar."

"But... perhaps the way of Hell seeking to corrupt another soul even more valuable to our Lord, if he is as you say."

Devils do serve the interests of Asmodeus; it is the way that they have been remade.

"I must consult with my superiors upon all this matter, and return to you.  I will write you the compact to take to the mortal; it will be well for him to sign, or so it would seem, even if we are not yet permitted to bargain with you or your price finds no takers.  Have you thoughts upon wise and cunning terms therein?"

"The aim is not to conceal things from him that require great intelligence or paranoia to notice; he has both, and we don't wish him to train either. The aim is to state in plain language the Evil he is eager to arrange for himself to do, stated so plainly that it does not occur to him it describes anything that ought to trouble him. Risks to his rights or his bank account he'll be looking for; risks to his Goodness he won't. He has claimed me as his possession in this life, and if he seeks to exercise the option it'd be for the same reason; because it inspires envy in him, to know that a part of what I am - a small part, he believes - is given forever to another, that they will have rights over me that mustn't shock his conscience but that can be permitted to stir his jealousy. 

I'll need to review it. People not accustomed to dealing with him make mistakes."

"The thought occurs to me that you might, perhaps, wish to sell him that option upon yourself.  It will not suffice to damn him, but it will be a start."

"The thought occurs to me that you might wish to make the option annullable by your returning of that payment to him, if he has not already exercised it.  While I do not know all your plans, I know that mortals often change them.  Perhaps you will find yourself plotting to execute a different compact with him in the future."

Keltham will be comfortable with that; Carissa is surprised that Hell recommends it. "I will bear that in mind." Actually, 'I asked the devil and he said he'd ask other devils for takers on the general contract, but said I should sell you, not give you, your option' will make Keltham feel positively about devils. 

He is not unmindful of Sevar's advantage over this mortal, if she serves Hell's interest more, and the terms he suggested are advantageous ones to her in future negotiations.  He will take what he can from Sevar for Hell; taking from her to advantage a non-Evil mortal is another matter.

"If you can seduce him to unmake and re-sign a different compact every three moons, on some excuse and tale of Hell's changing conditions, that will suffice to damn him before nine seasons pass - if he otherwise acts not for Good or Evil.  Remember me well in your reports, if it proves so."

Glosialabolas sets forth to design a compact so simple that it almost pains him.  Almost.  The devils of contracts do understand the concept of not overcomplicating and calling attention to a sting that requires neither attention nor complication.  At the core of all of this is that the mortal is suspicious of prices, rights, terms, conditions, but not that the very act of what he is doing is great Evil.

When he is done, Glosialabolas presents a compact to Carissa Sevar for an option upon her soul.

She doesn't say thank you, because that would be ridiculous. She reads through it, suggests a few small revisions to make it more like Lrilatha when she's trying to impress Keltham with the clarity and trustworthiness of her contract-writing, hands it back. Doesn't say anything aloud about it; devils are sensitive about being obliged to write honest contracts.

Who writes like that!?

Glosialabolas grumbles, but makes her suggested revisions; it's clear that Sevar knows too much about contracts, as she knows too much of other things.

"He'll ask, also, whether as I was taught I demanded reassurance that the terms of the contract conceal, to your knowledge, no clever traps and no terms with unexpected negative consequences for those who sign it. I think the unexpected negative consequence is not in the terms, and for precisely that reason will escape his notice, and if that's so I would convey your assurance of it."

"...it would do grave damage to the interests of Hell if it ever became believed that devils, asked such a thing, would not simply and absolutely refuse to bargain."

"Perhaps you know more of our Lord's workings here than I.  But can you truly assure me that this mortal's soul is worth the risk to Hell's reputation?"

"He has already secured such bargains, from devils apprised of his full nature and of as much as we understand of Asmodeus's direction."

By her soul's tilt she is being honest.  Glosialabolas thinks the equivalent of "Okay then, but still, the HECK?" in Infernal.

He amends another term or two and hands back the compact again.  "Tell the mortal that Glosialabolas, who made this compact, guaranteed this:  The deed that results from this contract's signing and its execution, will be as I expect that he will expect.  As for the consequences of the deed itself, time will show it."

"I will tell him so. May your other errand from me go as smoothly." That's probably pushing it, framing checking whether he can buy her soul as her errand she requested of him, but you have to push until you get a 'no' and she's very aware she hasn't, yet, gotten a 'no'.

Why yes, it is pushing it.

"Do not presume to rise above your given station.  You are not as yet the least of devils, whatever your soul's price to those who are."

"In three hours' time as it passes in Golarion, I will return to this place, perhaps in company if your price finds a taker or a bargainer, and if our Lord's will is in accordance this day.  Be there or be bereft."

Glosialabolas turns then at an angle, to return to Hell.  He has a most urgent plea for clarification to file, to his master and his master's masters.

Also, is he supposed to actually tell anyone in Golarion about the unfinished cleric thing.

"- right," says Carissa to the High Priestess. "Well. I'm inspired by Hell's apparent estimate of the value of our work. I guess I had better go talk to Keltham, then."

"Your will, Chosen of Asmodeus."  It sounds exactly as sincere as before; the one who says it was not previously a poor faker.

Subirachs has an urgent report to make to the Grand High Priestess's secretary regarding what Carissa Sevar's price is not obviously not, and also report the promise Subirachs made to Keltham regarding a test to run on Sevar if her soul cannot be sold for any reason.