"If a Dimension of Dreams is known to you, it strains credulity that it could be entirely unrelated to Parabola," allows Mr Cards, "The experiment would be well worth my time, as if brought there, it would not be difficult for me to confirm the connection. If Glasswork* functions in that place, there must be some relation... though tracing a route between the two may be a considerably longer task. Should a Fingerking have visited this realm earlier, it would almost certainly have been by possessing a dreamer or traveller. If there is indeed a connection between Parabola and your Dimension of Dreams, then it would be possible for a being thus possessed to make it easier for other beings of the Is-Not to follow in their path, making what may have been an accident into a more certain route. As to the specifics of that action..."
A moment of weighing, a conclusion that Mordessa has indeed revealed enough information to be worthy of this piece of intelligence. After all, it is arguably tied to their original agreement to suggest ways in which how such incursions might be prevented.
"The path to Parabola was opened by a pact between the Fingerkings and Hell. I am not privy to the exact wording of that pact," they say (somewhat misleadingly, since certain myths line up too well with what fragments of Hellish scripture they have accessed to be coincidence), "But I am aware that some part of Hell's obligations require that its Devil produce and distribute a drug known as Prisoner's Honey. I understand that this obligation has become quite profitable to Hell, though the specifics of that trade agreement from our end is handled by my fellow Master, Mr Spices. Regardless... in small quantities, consumption of Prisoner's Honey sends one's mind shallowly into Parabola, as if in vivid and lucid dream... where it can be more easily influenced by the Is-Not. In larger quantities, it can send one bodily into Parabola, through a mirror, and one who passes through a mirror thus can bring physical items and possessing entities through with them. As this is an old agreement, the Fingerkings have a great many agents of their own, and can easily smuggle more through any mirror they are aware of. Not every reflective surface is equally suitable for passage through to Parabola, as untried mirrors in new locations often lead to more dangerous parts of that realm... but a mirror that has seen successful passage is more easily found from Parabola thereafter, and it is not a complex application of Glasswork to use one mirror's position in Parabola to find other nearby mirrors. It would not take an infiltration of your Fortress to permit even accidental passage... merely a single successful trip through any nearby mirror."
"The chief precautions against this infiltration," they conclude, "Are to cover, guard, and regulate the use of mirrors, especially mirrors large enough to permit a human to pass through them, or in more sensitive locations. Additionally, it is useful to check the eyes of potentially susceptible individuals for a Viric** glow, which the ignorant sometimes mistake for simple green light; this serves as a somewhat reliable indication of outright possession, though mere influence is far harder to detect."
As to their bait, Mordessa's response is at once disappointing and interesting. Though she seems surprisingly willing to accept either possibility, she did reveal that her Hell is a monarchy... and specifically mentioned the name 'Asmodeus'. Not the same Hell, then... at the very least, the Devils they know of are certainly not a monarchy at this time, wherever it was they came from originally! And though they have certainly offered various aid and favours to the dethroned aristocrats of the Hell they are familiar with, they have no particular desire to see that faction triumph, and the support of foreign Devils seems likely to lead to complex and undesirable consequences. But perhaps... it would be useful to sow a seed of confusion here.
"As I had mentioned previously," begins Mr Cards, subtly invoking their talent for Mithridacy as they focus themselves on ways in which what they claim might be seen as true, as they watch Mordessa's own reactions for hints that they are along the right path, "You seem better informed than I as to what lies beyond the River." (After all, you claim certain knowledge of what lies after final death, and I merely have hints and visions of what the Boatman may become able to do in the future, now that I have fixed Death.)
"From a scientific perspective, such matters are mysterious and unprovable, since those who do not return from death are unable to provide evidence of what comes afterwards." (True, since vague memories of fleeting glimpses of the far shores while dead are hardly proper evidence.)
"More to the point, the Devils of my own world make far vaguer claims than you have on the nature and significance of the soul, for obvious reasons. The common claim is that the soul is a curiosity, a trifle, even a burden. They then offer a nominal sum to purchase the soul of any who are convinced by their arguments, claiming that such a transaction has no significant consequences in this life. These claims often prove persuasive, especially among the poor and the desperate, who often find even a rather trivial offer of immediate wealth more persuasive than a theological argument." (True, though much of Mr Cards' obvious contempt for such folly is lingering bitterness towards their own past foolishness.)
"More significant and powerful individuals are courted more carefully by Devils, and offered far greater prices, but the principle argument is the same... that there are no significant worldly consequences to the sale, and that there may indeed be some professional advantage in making such a deal. Solicitors***, for example, are commonly acknowledged to benefit considerably from such pacts, to the point that it is considered a stereotype of the profession." (Also true, though the additional detail is meant to lend verisimilitude to the proceeding argument.)
"This strategy has worked rather well for Hell, despite rival claims by the politically-powerful Anglican Church that those who lead wicked lives or sell their souls will be condemned to torment in Hell after their final death, while the pious and virtuous will instead ascend to Heaven." (These things are indeed so claimed. Mr Cards has more specific knowledge of Law Furnaces and the uses of souls than such laypersons, but that isn't relevant to their argument; they're illustrating a valid strategy used by Devils to claim souls in order to frame a degree of ignorance as to what happens afterwards.)
"This religious claim does indeed seem to align with your own description of the dead passing onto Hell or other afterlives beyond the River, though I would not previously have considered it a reliable claim, as I did not generally believe that the Anglicans were correct in their claims regarding the true nature of reality," (Despite social obligations, Mr Cards was not much of a churchgoer prior to selling their own soul, except as was necessary to fit in to polite society and avoid scandal... and though by 'previously' they more precisely mean 'at one point in my own past', as some of that disbelief had faded on unexpectedly recovering their soul at the hands of a surprisingly capable Church-backed espionage operation, they were and are not quite the sort of person willing to wholly embrace a faith-based 'God works in mysterious ways' argument as justification for the lack of more overt evidence of divine power. Not after having seen the Mountain of Light, at least.)
"Regardless, I had considered such things largely irrelevant to my own self, as I do not expect to permanently die. Among other things I have considerable assurances regarding my own survival for at least the next couple of centuries, beyond which point I expect to be able to access greater protections still." (The point is to present this as a comparatively unimportant subject to them personally... but this is still actually true, on reflection. Once they have properly become a Curator, Mr Cards expects a lifespan at least in the tens of thousands of years, if not improved further by the Hesperidean Cider. And even beyond their own longevity as a Curator, Mr Cards will return to Irem; this is true prophecy, if anything in the Neath is. They will come once again to the Crossroads beneath the Seven-Serpent. There, they will reach along the threads of destiny to tie knots in their own fate, those knots which they will remember having seen when first they set their hands upon the threads of their own destiny, but which they had not yet remembered tying. If they permanently die before their return to Irem, their past will become inconsistent with their foretold future. This is paradox, and so it must instead be the case that Mr Cards will return to Irem... provided that their interpretation of those visions is correct, and that their trip here did not somehow invalidate their Destiny, at least. Wiser perhaps not to test matters beneath the light of an unfamiliar Judgment enforcing a different set of Laws, to be sure.)
"Still, the Devils presently in London do not often attempt to explain the nature of Hell, preferring instead to make hints and vague references, in keeping with their apparent strategy of deliberate misinformation." (True, though such hints and references are more useful than Cards is implying.)
"Nonetheless, some hints and older written works do line up in the same direction. For instance, I have indeed heard of Asmodeus, King of Hell," (in Lemegeton Clavicula Salomonis, a work that more serious scholars agree to be deliberately obscurantist, and written or influenced by Devils to present a misleading view of Hell's organization and structure... though some Devils have certainly claimed some names from that book as their own.)
"I have also heard the organization of Hell described along approximately aristocratic lines, with various noble titles being granted to powerful Devils who rule parts of Hell, and are themselves subject to still greater Devils with greater power and authority, and so on." (From representatives of the defeated Brimstone Convention, who no longer hold power, describing what Hell was or ought to still be.)
"I would not ordinarily consider various sources purporting to describe Hell in greater detail to be especially reliable, though some older religious works famously go into considerable detail in their description of nine sub-areas of Hell," (La Divina Commedia and works inspired by it are widely considered fictional, and so are indeed not considered reliable by Mr Cards, however relevant that structure is to the conversational point at hand.)
"You have, for your own part, been more informative about such matters than those Devils I have spoken with previously, which suggests to me that you are under different restrictions as to what information may be shared than they are." (True, trivially so if they are receiving orders from entirely different Hells, though 'different orders' was previously framed as an alternative to 'different Hells', and so ought to feel like a more salient point with so many true supporting reasons to believe it. Still, even if their standard 'talking to Devils' conversational ploy in presenting themselves as a largely amoral researcher is not quite perfect, as they have yet to truly abandon their human sentimentality... their emotional reaction to how how useful Mordessa is being is certainly genuine.)
*: Techniques for manipulation of mirrors and dreams
**: The colour of shallow sleep; also associated with growth, infatuation, and vegetation.
***: Professionals who handle legal matters and oversee court proceedings for their clients, implying a legal system too complex for the layperson to navigate unaided.