The proprietor of this store is a noble Efreeti who stands tall even for a noble, currently bargaining with an even larger Brutalis devil over a heavily magicked sword that Carissa couldn't lift with a Bull's Strength.

Serving as store assistant is an Azer - a brass-skinned dwarfoid native to Elemental Fire, whose hair and beard trail off into solid flame.  Almost all of Azerkind are enslaved by the Efreet, for the Azer's citadels were distant and had poor relations with one another, so that the Efreet armies could fall on their cities one by one and enslave them, without the next city becoming any the wiser.

The Azer assistant will inform Carissa that the price of the Ioun Stone proudly displayed in the store's window is -

- well, Carissa can either blow her whole remaining budget on that one Ioun Stone.  Or she could try to meet Keltham's conditions of secrecy and known use, to trade a Wish diamond.

....she should in fact do this AFTER she is smarter and not before. If she feels on some level like her greater Wisdom will lead her to not buy the ioun stone, that's because she actually shouldn't.

And if she should, she will. 

Before Carissa can go, the Azer will inform her in a low confidential voice that if the Ioun Stone orbiting in the store display caught her eye, there's an Orange Prism Ioun Stone that can be brought forth for the truly discriminating buyer.  It would increase the power of all her spells by about half a caster circle, including when it came to determining what sort of spells she can Permanency.

Well, how does this shop feel about Keltham's confidentiality agreement.

The huge malik (noble efreeti) and the huger devil don't seem to be coming to terms on the enormous +2 keen wounding sword.

The giant devil, of dull-golden hide, whose head and shoulders are both crowned and crested with many horns, turns away finally from the bargaining counter.

"He overcharges, even more than do most of his kind," the devil says in Infernal to Carissa Sevar.  "It seems he has some prejudice against Hell and Hell's."

The devil's voice sounds exactly like Carissa's father.

And Carissa feels a surge of hatred towards those awful price-gouging lol no Carissa has a Mind Blank up.

"Maybe," she says dryly. "Or maybe he overcharges everyone, or maybe it's just you; we'd have to observe some other transaction to see."

This is dangerous, this is really genuinely dangerous, but Carissa Sevar, these days, is fearless; the worst thing that can happen by her values is nothing on this trip going wrong.

The devil's eyes linger on the artifact crown of this woman, as seems to be the make of Hell; who replied to him in Infernal, who perhaps has bought fair form of some Hellish fleshcrafter, who seems to have absolutely no fear of him at all.  Even her surly tiefling attendant is equipped surpassingly well, though without any artifacts of her own.

"Have you need of some little service while you are in this City, perhaps?" the devil inquires smoothly.

Odds it's a trap or a game of some kind - what is she talking about odds. Of course it is. "My business here is so secret that I will speak of it to no one who hasn't sworn me confidentiality, on not just what I'm buying and what I'm paying but of every matter they learn in the course of our transaction."

"And if I promised confidentiality from all the inhabitants of this city, but not from my superiors in Hell?"

"No deal."

"Fascinating.  I hope it's not a problem if I report this discussion to my superiors?"

"As they please."

"Is there a name, then, under which I should report of this matter?"

"Carissa Sevar, Dispater's. Should I have yours, in case some future business of mine on the Material could use it?"

There's no sign he recognizes her name.  "Barbulbumalphas, of the Platform of Searing Irons in Stygia."

The devil turns from her, and exits the store without further speech.

The noble Efreeti (that is a 'Malik' of Efreet, in their own tongue) has been watching all this with an aloof expression, like a father watching the squabbling of two children, neither of them his own -

- well, until she claims to be Dispater's, and then, possibly, his face twitches a little.

"Your business here?" he inquires in Infernal, in a voice that sounds like heated brass feels to the touch.

"Well, do you agree to swear to confidentiality, about the content of our negotiation and anything that might be learned in the course of it?"

"I can so swear, if you intend to make a purchase here."

Yay!!!!!!!! She's going to have so much magical bling -

- when she dies.

Her face is not expressive, obviously. "I do so intend."

"Then so long as your intent proves true, I swear to keep secret the content of our negotiation and all that I learn from you in the course of it, save what I must answer to officers of our city to prove to them that I obeyed our city's laws."

"If we are unable to arrive at a purchase agreement, the confidentiality must still hold."

Tarnish receives a message back from Ri-Dul, relayed of Keltham, who can't be in the Telepathic Bond because of Mind Blank.

"It must also apply to anything you learn from me, whether by speech or by purporting to read me.  It applies to anything you may have already learned or guessed from watching us.  All that passes within this store, as we now occupy, while we occupy and occupied it, is of the negotiation.  Your servant will also swear and must be sent out during the remaining proceedings.  You represent that you neither know nor suspect of others listening to us.  You may swear to the officers of the city no more than that you have obeyed the city's law."

The Malik's eyes narrow, and from his throat comes a brazen laugh.  "Stringent conditions indeed, if I may not report on what I've already learned and what a devil already knows.  Do you, perhaps, offer me some token of payment, to cover the event where we do not arrive at a purchase agreement after all?"