If you're going to assassinate the Queen of Cheliax, you'd better be very thorough.

The assassins, unfortunately, will be condemned to the worst tortures Hell has to offer, for failing to retrieve the Crown of Infernal Majesty first. That their hands were constrained by tropes is not an excuse their souls' owners will be inclined to accept, if they even understood it.

Luckily, they're not very real, even compared to the other characters in this story.

In a secret city in dath ilan, in a lavish (by Chelaxian standards) and not very doompunk (again by Chelaxian standards) apartment belonging to a certain Law-Abiding Sociopath, an infohazardously beautiful woman in an elaborate doompunk outfit appears from nothing.

She takes a look at the apartment's occupant.

"Okay, what the fuck, Aspexia?"

"Tsi-imbi," says the woman who looks exactly like Aspexia Rugatonn, in a language that is definitely not Taldane.

The word doesn't have a direct translation in any language of Golarion, but Abrogail's permanent Tongues gives her the gist of it.

"Yes, you almost certainly have gone insane," she says, "but that really does not answer what the fuck from my perspective, here."

"I don't think anyone heard me," she says, taking out her phone. "I really ought to tell someone about this; if I am having immersive hallucinations, my not telling anyone about it presents a rather larger risk of the destruction of the world than I'm comfortable with. On the other hand, in those worlds where you are real, you're in an extraordinarily restricted area and if I tell anyone about you you'll be involuntarily cryosuspended for materializing into it. If you'd rather that not happen you have thirty seconds to convince me this is reality."

No one turns Abrogail Thrune into a statue. That's her thing.

"I would, if I were inclined to believe that myself. Impersonating the Grand High Priestess is punishable by Malediction, is what I would say, if I had any confidence I were still in Golarion at all."

Appearing to know you personally is, she knows, a common feature of hallucinations. Appearing to doubt their own reality is not. It actually raises the probability that this person, even if a hallucination, is self-aware. Not that she'd care, the way most dath ilani would, and even most dath ilani would agree that you have two and a half seconds to kill the self-aware tulpa in the evil Keeper's head, but it does shift Athpechya's highest-expected-utility action slightly in favor of not alerting anyone yet.

"You are not in 'Golarion'," she says. "I have never met you before. Why do you believe you know me?"

Something occurs to her, a possibility the Keepers sometimes speak of almost jokingly; Civilization's actions would be very different, if they really believed it.

"Did you experience dying just before you appeared here?"

"It was an involuntary Plane Shift, or a Wish-kidnapping, or something in that genre," she says. "I did think someone was trying to assassinate me, and then when I arrived here I thought the Grand High Priestess, who looks exactly like you, was pulling some sort of elaborate prank, and now I have no idea (in Baseline, 'plenty of evidence and no hypotheses') what the fuck is going on."

Several of those words didn't translate, but some that did hinted at this woman having arrived from an economicmagic fantasy setting, which is the opposite of the way it's supposed to work, but whatever.

"I believe that we are in a story-where-the-protagonist's-subjective-thread-of-experience-continues-in-another-world-after-their-True-Death*," she says. "It is theorized here in dath ilan, that those who die here may continue to exist in such a fashion, though I had not expected anyone to appear here. It would suggest that dath ilan itself were a story or simulation, which is contrary to all previously known evidence. If my inferences are correct, you are from a world with economicmagic which I, as one of the presumable protagonists of this story, would be happier inclusive-or more interesting in, perhaps one that's less oppressively Good. I am curious as to what the 'Grand High Priestess', the person who supposedly looks exactly like me, is doing in your world. The word did not quite translate."

*This is a three-syllable word in Baseline and Japanese.

The probability of this being the actual Aspexia Rugatonn, the one with the power to make her life quite unpleasant, is now low enough that value of information is the stronger consideration.

Detect Thoughts.

Athpechya has INT and WIS scores that do not occur in unenhanced Golarion humans at all, and is otherwise a complete commoner.

The spell goes through.

Her thoughts are organized, precise, in a way that no thoughts Abrogail has ever read before are, made of numbers and explicit probabilities, constantly tracking across many possible worlds. One of the foremost threads of her attention is devoted to the question of whether Abrogail really exists; she currently places that at 80%, conditional on "existence" actually meaning something real at all anymore. Several more threads are devoted to elaborate planning in the worlds where Abrogail is an ally, and the worlds where she's an enemy.

She does appear to be Aspexia Rugatonn, if Aspexia had been raised in a totalitarian Lawful Good society without gods or magic. And she's trying to—they're trying to build—

Suddenly, in a moment of wordless inference, Athpechya connects the expression currently on Abrogail's face with the gesture and incantation she made earlier, and her mind goes completely blank.

"Are you reading my mind?" she asks, thinking this and nothing else.

She dials the phone.

"Tsi-imbi, and I need security capable of dealing with an adversary with unknown psionic abilities including mindreading if I am in fact sane."

When security arrives, they find a very detailed stone statue of Athpechya, and no Abrogail Thrune.

First, though, they flood the apartment with sedative gas. Dath ilan doesn't send corruptible human security to respond to a tsi-imbi in the Basement of the World until all potentially insane parties are safely unconscious, even if there weren't a potential mindreading sorceress involved.

It's the sort of gas that affects your perception first, so you don't notice until it's too late. If Abrogail is hiding in the apartment, she needs to make a Perception check.

Lol.

Abrogail's Crown is an item of poison immunity among its other functions.

She casts Gaseous Form to make sure the outline of her body isn't visible in the haze.

Elite dath ilani Security are, in fact, trained to respond to adversaries with a wide variety of alternatephysics abilities, mostly because this is the sort of thing that very smart dath ilani Exception Handling planners do for fun when they've exhausted all the so-called realistic possibilities (and sometimes even when they haven't quite), but also because the eighth-rank Keeper in charge of designing the security systems for Civilization's most important projects, who is one of five people in dath ilan cleared to know the true nature of Reality*, assigns weirdly high probabilities to this occurrence.

Athpechya warned against mindreading specifically, so the team that responds, while not Keepers themselves, has trained extensively in the Keeper arts of thought-control, and is also wearing helmets lined with depleted uranium, in the (likelier) case that the mindreading is just Sufficiently Advanced Technology, or else that this is the sort of alternatephysics that pretends to respect realphysics because the author thinks that's clever.

*A secret hypothesized to destroy the world if too many people merely think about it.

The possible worlds in this situation are mostly divided into those where Athpechya was telling the truth and those where she wasn't. Both of these are so unlikely on priors that it isn't considered worthwhile to even attempt to assign explicit probabilities right now. Overwhelming evidence for one, the other, or neither will be found eventually. In the meantime, that isn't Security's job; Security's job is to secure all possible worlds.

In that case, they need to apprehend both a rogue sociopathic Keeper and an unknown intruder with alternatephysics powers including but not limited to mindreading and presumably teleportation. (These powers don't usually appear together in dath ilani stories, which prefer to explore the implications of economicmagic and mentalmagic separately, but the relevantly cleared Keeper who planned Basement security wasn't expecting dath ilani tropes anyway.)

—this is the Basement of the World. They haven't drilled this exact scenario, but they do have protocols for each factor separately.

(Athpechya's agreement with Civilization included no additional security burden beyond that of an ordinary first-rank Keeper, but they sure do have more detailed plans for this specific contingency than for any other possible defection.)

The Basement does not in fact have counter-mentalmagic-trained Security on standby in every apartment block, so it takes three precious minutes after the alarm to get them on site before the block can be hermetically sealed.

You can't get out of the Basement of the World in three minutes. The site is already by default as close to causally isolated from the outside world as its operations permit. Within seconds of the alarm that isolation is complete. The tunnel that connects the site with the Keepers' headquarters in Default, the only path by which people and materiel may enter or leave, is sealed by multiple sets of blast doors on both ends, the spaces between the doors randomly either filled with toxic gas or heated to thousands of degrees. The Faraday cage over the entire installation that already prevents radio signals from entering or leaving the site's few surface buildings is supplemented by an unfolding canopy of flexible radiation-absorbing material that will block off the rest of the electromagnetic spectrum as well. The closely monitored fiber-optic relay which is the Basement's only legitimate connection to the Network is physically destroyed.

—on the independent authorization of any two of the Basement's director (an immortal ninth-rank Keeper named Leareth), deputy director (an eighth-rank Keeper), and assigned Meta-Keeper, the entire installation will be instantly reduced to a large radioactive crater.

If Athpechya had somehow managed to leave the Basement on foot, she would still be surrounded by hundreds of miles of virtually impassable and entirely uninhabited jungle. A handful of people in dath ilan have the level of Wilderness Survival training necessary to have more than a 10% chance of making it back to Civilization from the Basement (or, as is the more usual concern, vice versa). Athpechya is not one of them, and she would not in fact be permitted to receive such training if she asked for it—even if she didn't work in the Basement. It's a controversial policy in dath ilan, to gate the ability to truly opt out of Civilization on sufficient Moral Integrity (and permanent sterilization), but they are in fact suspicious of why anyone would want to move beyond the reach of even the utterly minimal law enforcement of the Last Resort.

The overwhelmingly most likely possibilities, therefore, in the worlds where this is a nefarious plot of Athpechya's, are either that she's still in the Basement, or that she was already gone before the alarm was ever raised. They know that the alarm came from Athpechya's phone in Athpechya's apartment, but they can't instantly verify that the phone wasn't tampered with to send a prerecorded message. By the time they can do that, they'll have access to the sealed camera footage of her apartment anyway.

—they can't actually tell the rest of Civilization to be on the lookout for Athpechya while the installation is on lockdown. That's an accepted cost of potentially having a hostile superintelligence in your Basement. So that world's Security response for now is focused on locating her within or immediately around the Basement. If she's there, it shouldn't take long.

As for the unknown mage, the ability to get in implies the ability to get out. Being already inside dath ilan's most secure facility and possibly unfamiliar with the broader world, they would likely prefer not to leave, but the simpler explanation for their observed absence is that they teleported away when the gas started. If they are still here, invisibility and poison resistance must be added to the list of their known powers.

(There might be debates, among ordinary dath ilani, as to whether it's a valid use of the Simplicity Prior, what another world calls Ockham's Razor, to assign the former world higher probability. A Keeper would simply know that the answer is 'no'. One true violation of the known paradigm of Reality is evidence for the possibility of arbitrary violations.)

The commander of the Security on-site doesn't actually assign very high probability to being able to apprehend the unknown mage, even conditional on them actually existing, so the obvious next priority is to recover the statue which might by some unknown mechanism contain Athpechya's soul.

Uh...no.

Circle of Death.

Of the nine Security in the room, one makes his save.

"People down, unknown weapon, need backup immediately," he says over his radio, in a secret conlang known only to Basement Security. "Possible invisible assailant, get some inert fog in here."

(The conlang is only useful in the worlds where the helmets are effective against mindreading—)

(—which includes this one, but—)

(—the Baseline word for magic is 'alternatephysics', not 'alternateinformationtheory'. Even given a trope-governed universe, dath ilan assigns much lower probability to the existence of truly sourceless translation magic. Such a thing exists at all in dath ilani fiction, but you wouldn't put it in a novel that was trying to look like it particularly cared about coherent worldbuilding.)

(Abrogail does not give a flying superheated shit what a dath ilani audience would think of her powers.)

She could cast Gaseous Form again and hide from the fog. She could also just massacre all of the Basement's remaining security and then do whatever she wants.

Nah, no fun.

She Disintegrates the surviving Security, and has maybe one round before backup arrives.