"Interesting idea, Abarco," says Commander Hadrian.

This fucking idiot.  Abarco did not need to say that out loud.  Well, Abarco will realize how he fucked up, once he gets the telepathic message that was already en route to relay, ordering Abarco silently to stay out of the Plane Shift so that a traitorous Sevar could just land on him.

(Partially it's his own fault, Hadrian is a fresh commander over Abarco and shouldn't have assumed Abarco knew Hadrian for a competent commander who'd think of that; should've warned Abarco of the plan by relay, before Hadrian said out loud that he was going along with it.  Not that this forgives anything.)

"You have foiled the brilliant stroke of my master plan to pass up dozens of opportunities to desert, demand to sell my soul, do so, and then immediately desert," she says dryly. 

They reach the edge of the Forbiddance. Rescue Teleport, Keltham? No?

Even at INT 24, you can't predict a sequence of events like that, or time it precisely when somebody is in a scry-screened area.  INT 24 is not enough to knock billiards into billiards and make trick shots deliberately.

In fact, that person's strategy was skewed towards exploration rather than exploitation, as makes more sense at the beginning of a task, where information is at its most valuable when amortized over all remaining time.

His plan was mostly that he would poke Cheliax and then observe what happened next using a pair of Discern Locations on the subsequent movements of Carissa Sevar and Abrogail Thrune.

The result of the Discern Locations were that Carissa Sevar was moved to beneath Asmodeus's temple in Ostenso and Abrogail Thrune was Mind-Blanked.  This does narrow down a lot of previously-probable-from-his-perspective variance-in-possible-worlds.

Based on the prior exhibited competence of Cheliax, and their lack of any established fictional genre or real-life history about dath-ilani-style dueling geniuses, he does not expect that Cheliax has deduced what he's doing, deduced his probable table of probable possibilities, figured out his sensory modality is Discern Location, and selected a response optimized over the update he'll make as a result.  Augmented Golarion mortals do not appear to be that smart, they do not know the direction in which to try to be that smart even if they have the theoretical brainpower for it.

He's going to track that possibility anyways, of course, that they have visualized him partially or in toto and optimized a response to update him in their preferred direction.  Abrogail Thrune wouldn't have planned that far in advance, the Conspiracy didn't plan that far in advance, but Carissa Sevar has now had serious dath ilani exposure and been issued an artifact headband.

INT 24 isn't enough to predict a sequence of events like that.  It is enough to list out lots of possibilities and optimize over the probable ones.

That person did explicitly consider that Carissa, having obtained an artifact headband, had been cognitively perturbed, and might defect from Cheliax once out of her previous state of mind.

That person did moreover explicitly consider that Carissa might be more ripe for defection from Cheliax if she was put into a situation where her mind was knowably-to-her probably not being read, such as a situation which prompted high-powered Nondetection, or Mind Blank.

This situation - as is, in fact, not exactly what has occurred - was his major possibility #5, subpossibility #5.3.  Probability 3%.

That person credits 'tropes' less than he once did, having worked out some of the hidden rails of causality underneath, that gods were meddling too.  But he assigns weird coincidences a higher probability than if he hadn't run into all the weird shit he had.  Something is messing with probability around this planet.

It is worth the extra effort to give that force some small boosts and opportunities to mess in his favor, if it happens to be so inclined.  That 3% chance is not the only equivalence-class of outcome where Carissa Sevar defects for some reason, today, as a result of causality playing out from his plan.

Therefore, that person has placed himself where he can hear a Sending (he's protected against Demands, obviously).

And he also timed his probe by when - according to Ione Sala's allowable pre-Nefreti knowledge - Carissa Sevar would just be waking up, if she was sleeping according to her usual Ring of Sustenance habits.  He timed it for then plus 20 minutes.  That, he reasoned, ought to prevent Carissa from having already hung spells that day; and would give Carissa a chance to hang spells useful in defecting, if she ended up put under a Mind Blank to prevent Wishnapping by him, and the artifact headband boosts made her realize that serving Asmodeus was stupid.

INT 24 is not enough to predict an exact sequence of events.

So that outcome is not mostly what that person expects to happen.  He's not going to show up with a mercenary army unless Carissa manages to call him about that, or signal him in any number of possible ways.  There's all kinds of possible ways for Carissa to escape once Mind Blanked, right?  Probably the tropes will be with her.

If the only result of things playing out like that is for Carissa to break with Asmodeus, but find herself with no clever options besides confessing the fact to Cheliax before they Detect her thoughts about it, they'll presumably employ her the way Asmodia was employed, or put her into storage to trade to him.  In this case they no longer have a high-level ilani augment of their own to oppose him.  That isn't his optimally desired outcome, but it's an improvement over status quo ante.

Besides the information gained by Discern Location, most of that person's positive expectations of probe results are about cases where Cheliax initiates negotations with him to not destroy Cheliax.  What actually happened instead, here, is not something where he could afterwards say, "all according to plan".  But that's how it goes when you're merely INT 24.

And now Hadrian has to make a call.  Actually leave Abarco behind?  With Sevar forewarned, she wouldn't be catchable that way...

Or he could secretly order Abarco to come with, and bet on Sevar not being sufficiently confident of his doing that, to stay behind, if she's a traitor.  Which she probably isn't, and Abarco is potentially pretty useful in Hell... of course, the traitorous Sevar would expect him to reason like that...

Eh.  Sevar's point about not being predictable to ilani is well-taken.

Hadrian orders over telepathic bond for base to spin some coins or roll a die, whichever they can get to immediately, and have Abarco stay behind with 1/4 or 1/3 probability.

Commander Hadrian doesn't have a fancy artifact headband, but he does have native INT 17 and a +6 headband and has read some Project Lawful Transcripts, so he's not wholly at sea in this crowd.

She really is going to miss it here. She takes Hadrian's hand, and Olegario's, and does not resist the Plane Shift.

Resist Energy (fire) for everyone.  Air Bubble for everyone.

Plane Shift to Avernus for everyone, roughly targeting an area he knows Cheliax sometimes passes through.  Abarco can stay behind if the probabilities went that way.

They came out in favor of his coming with. He's here. 

Carissa rolls her eyes at him. "My Teleport, I've been at this site most recently?"

It's not Hadrian's first time in Hell, but the endless background screaming isn't any less disturbing a second time.

They're no longer in a Mage's Private Sanctum.  He could Dispel his Nondetection on Sevar, order her to fail her Will Save against Detect Thoughts... the hypothetical enemy probably couldn't nail a Scry on her in a short time window... but he does not have prepped another of his more metamagiced Nondetections.  Realistically, they are in Hell, it is a dangerous place, Sevar has just sold her soul of her own will, and this will probably go better if they put aside some hesitations and work together.

"Go ahead and try it," he tells Sevar.  If she fucks up her very first Teleport, they'll not be any more lost than they are already.

It's worse without the Planar Adaptation.

It's better with the knowledge that she needs to overthrow Asmodeus.

Carissa tries to hold in her mind the image of the fortress she left from just a few days ago, and Teleport the four of them.

aaaaand in fact fucks it up. Well. Not that badly. This is the fortress but she managed to zap them all with discharging spell energy along the way, severely enough to kill a normal person but not actually all that badly for some fifth circle casters. 

- sorry, she almost says before she remembers she is Carissa Sevar and not the most junior member of this excursion. She will simply pretend that didn't happen, like any dignified Chelish person would.

"Anyone hit by that hard enough we should Infernal Heal?"

(no)

"All right, Sevar, what do we do here?"

"Rugatonn did the talking. They all ask, do you offer a payment or a threat, and she said, 'I am the High Priestess of Asmodeus in Golarion about Asmodeus's business; you will serve me as is your duty,' and then they each let us through. I can talk, if you think they won't back off for you."

Hadrian weighs possibilities, concludes that with them being in literal Hell and headed to Dis he's mostly going to have to play this on the assumption Sevar isn't planning to betray them all.

"You'd know better than me whether devils would be more likely to back off for me or you... unless you don't know, in which case my guess is that our strongest threat does the talking, so that's me.  How do we get the outer gate to open at all?  I don't see anything resembling a knocker."

"Aspexia Rugatonn just....knocked. The result was very loud, she might secretly have a strength of 30 or something. I don't know who devils would be likelier to back off for."

"I'll do the talking, I guess."  He knocks on the door... with an Admonishing Ray, he's not going to need nonlethal damage for anything else in Hell.

After a pause, the fortress door swings open, and a being comes forth like a withered cadavar made of bone.

Its eyes pass over the other mortals out of Cheliax, even the one stronger than itself; settles upon that mortal who was previously escorted by a 9th-circle priestess of Asmodeus and spoke before her, and now returns with a mighty crown of Hell upon her brow.

It waits for the strongest to speak.

"Hadrian of Cheliax, as is Asmodeus's country in Golarion and serves Him.  I am here escorting Carissa Sevar, who is named favored soul of Dispater, and we require entry to Dis."

Carissa Sevar stands impassive and motionless behind him. 

And behind her, a Silent Image in Infernal reads, 'they are not serve me, and should not pass alive.'

One of the verbs is conjugated slightly wrong, not in a way that changes the meaning. Carissa was never very good at infernal.

"Enter then," it says to them all, and behind it the second doors of the fortress swing open, revealing the nightmare of chains and gears that guides the maze.

Maybe it's easier when you've got Dispater's favored with you, instead of just Aspexia Rugatonn.  The politics of Hell often have little respect for Golarion's ranks.

Hadrian enters, assuming the others will follow him.