He says "fire and brimstone" as if that's what the arrows are made of... or simply the fact he believes these arrows can send demons back to Hell.
The demon is definitely being pierced by the arrows, but they don't stop its ability to shapeshift and attack. It sends out a snake-shaped "appendage", which dodges several arrows but finally gets hit with one. Meanwhile, the demon just accuses this guy of having no manners. The guy responds as if the souls of mankind are "greasy meals", whereas he himself is fine with cheap wine and stale bread. He even tells the demon it can "shove them greasy meals of yours where the sun don't shine". 😆 But I don't think he's quite thought that through, since, within the context of what's actually happening, he's telling the demon to shove souls up its ass.
But the demon's complaint isn't all that reasonable, either. Sure, no one really wants their meal to be interrupted, but it claims it's waited "so long for this dinner". This demon just started fooling Anna (and Modri) into believing its deception, as well as tricking wishes out of Anna, within the past few days. That's nothing compared to the wait Sebastian is perfectly willing to endure for just one more course (real Ciel being the appetizer and our earl being the planned main course).
Then the demon realizes the guy must be from a group of "buffoonish" humans who think they can destroy devils/demons. Then it recalls the name of that group: the Roman Curia Exorcists. (I'll talk about that name after the six chapter pages included here.) (edited)
I'm wondering if there's a slight mistranslation here, since the guy says it's impressive that devils in the "boonies" would know about their group after more than a century. Wouldn't it be more impressive if they'd heard of this group in less than a century? Perhaps he means "little more than a hundred years", which would make more sense. I suppose he's then talking about cardinals who founded the group... and who must have died long ago, unable to receive this news.
The demon, speaking from the head of a wolf or dog, sarcastically praises the guy and all the others in his group for believing anything a demon says. It's possible the guy doesn't actually know where the idea came from. The founding members might have truly believed some demon that silver is a weakness for demons (like it's supposed to be for werewolves). The impulsivity suggests whatever demon gave humans that false info did so without thinking of the possible outcomes or consequences. Is it sure that's what happened? Why not a demon deliberately lying about demonic weaknesses, instead of just blurting it out on the spot? Idk. Either this demon knows the specific source and reason for this false info... or it's just making an assumption.
Anyway, it says those crossbows with silver arrows are mere "toys".
Major edit: I must have skipped a page when I was reading the English translation of my copy, so I forgot to screenshot it, as well. Here's what got left out earlier. The demon taunts this guy by calling him the "red sauce" (colloquial term for tomato ketchup) for its dinner, as what appears to be a single arrow flies toward it. This arrow pierces the demon squarely in what could be called its chest. At first, it's just offended by the interruption. But while complaining about said interruption, its goop starts to drip. Then there is an audible sizzle, as it's forming a crow shape while some kind of smoke or fume starts to rise.
Major edit continues: In the previous chapter, we see an eyeball pop off from the demon, due to an attack from that weapon. Back then, the demon says nothing about a lack of ability to restore its form. This latest arrow must be different; maybe it is not simply made of silver, or perhaps the tip has been dipped in something potent. Either way, the result is significantly different from before, and the demon acknowledges (but is very confused) that it's unable to restore its body. We see it try to form another animal shape (octopus) while that smoke keeps rising.
I suspect the Roman Curia Exorcists have discovered some compound or chemical reaction that is way beyond anything the demon expects this group to be capable of producing/using. I wonder what sort of chemical this is, why it's actually somewhat effective, and how it causes this slightly delayed reaction. 🤔 🧐 🤔 (Major edit concluded.)
The guy asks this demon if it's excited/"thrilled" by such "toys" then claims he will teach the demon a lesson to respect mankind and "God". The demon emphasizes there's nothing divine about the weapon being used against it. However, it doesn't want to deal with two humans right now, especially since the souls it has already devoured are filling enough. It then threatens to return later for "dessert" (Modri's soul).
So, it slinks away, right through the floor, while crassly thanking them "for the meal".
Modri doesn't want the demon to leave just yet. He is just about to wish for something when the exorcist dude shows up. We don't know what he was about to ask for. He also hasn't taken revenge on the demon for what it has done to Anna and the other victims.
Hearing this story, either Sebastian or John Brown could be the one who reacts with remembrance, acknowledgement... and a renewed desire to finally have that dessert. If either one is the demon from Modri's past. It could be neither of them, but for his story to be pertinent to the main story, it really should be someone in the room. I would personally love it if Sebastian still has no recollection of Modri or these accusations against him... while John Brown shows signs of increased interest in Modri and/or his tale. I keep imagining John Brown's whole demeanor changing, and possibly even his appearance changing slightly, as he snickers and says something like it being "dessert time, at last."
Regarding the Roman Curia Exorcists, this is loosely based on historical data. The Roman Curia is basically the highest level group of administrative institutions that serve various functions for the Catholic Church.
From a FB page called "MY CATHOLIC FAITH (Knowledge of the Faith)", I found a detailed post about the Roman Curia. (I originally had five screenshots from the FB page here, but I needed to add in a missing page from the chapter. For more information on the Roman Curia, please see that FB page or some other source of information on the subject.)
At the end of their FB post on this topic, there's a link for the source they used.
I had hoped to post all of ch227 (translated) yesterday (18th), but I needed sleep, and these posts take time (and tend to send me down online rabbit holes), so I have now only posted 2 parts.