All right, back from the food poisoning… (Nothing to do with street vendors, idnlun–I think alas it was parma ham from a very good Italian restaurant, at which we’ve eaten several times before with no ill effect.)
I’m glad that’s been spontaneously suggested; I was worried that no one would see it as a meaningful option at all.
In response to your other questions, regrowing an eye takes more aether than an eyeball contains, and also more than any one Theurge could burn in “organic” blood without passing out, so there’s no industrial-scale blinding/regrowing solution. You really don’t want a collaborative process of eyeball-regrowing; it’s impossible to coordinate that kind of Theurgy with precision. Having four mages each trying to regrow a quarter-eyeball would result in something blind and bubbly.
No Theurge can use someone else’s living blood to make a Change, however close the proximity. There is a finite amount of aether in each person; it’s quickly run down during Theurgy, and once you begin to draw on your brain-supply rather than just your blood-supply, you pass out. But as long as you don’t make a suicidal push to burn all your aether, it will regenerate over the course of a few days.
Finding the most efficient practical applications of Theurgic insights does involve a fair amount of experimentation, and grasping a thing’s telos involves a great deal of study (sometimes empirical). So I wouldn’t call the Hegemony entirely unscientific.
But as with gunpowder weapons, the development of engines running on combustible fuels has been completely sidelined by Theurgy; there’s just been no reason anyone would develop something so fiddly to drive a loom or a sawmill when blood does the trick. Waterpower is widely used, but when there isn’t a good stream available, there’s not a lot in the Hegemony’s technological imagination that could take the place of blood.
Just a note for those who weren’t with us on the WiP thread: air rifles are a thing in the gameworld (as they were from a surpriisingly early point in ours), and have been mentioned obliquely in Game 1 as an anti-Theurge weapon:
“You’ve spent many an hour mentally running through other things that might work in theory [to defeat Theurges in Ch 4]. Things you’ve only heard of from listening to conversations in the agora, and can barely imagine: ${erretsin} wind-spitters, or a ballista, or a catapult loaded with hot sand.”
A few “wind-spitters” (ventisputori) will indeed show up in Grand Shayard in Game 2. They’re not produced on an industrial scale, nor really anywhere outside Erezza… but they’re one possible tool for a high-COM rebel and her trained band to take out Theurges from cover.
Overwhelming numbers of mages? No. But please don’t expect any army of mindless zombies to lurch out of the north across the Ward either. My George Martin homage only goes so far. 
I don’t believe anything I’ve said so far about them connotes shambling, unthinking hordes, or “converting the locals into Deadheads.” The main one Archlich Ghaesh will be interested in converting is you, and in more of a Richard Dawkins way than a Richard Matheson way.
Which doesn’t necessarily make them less of a threat. But we’ll get more detail on that later in Game 2.
Absolutely. Cyclical and predictable change (of e.g. seasons or generations) is no inherent threat to the eternal and unchanging Order of Xthonos–it’s just one manifestation of that Order at our muddy little tier of reality, far removed from the perfect immobility of Xthonos Itself. Change does carry risks, of course (any ordered change is to some degree a Doorway to Xaos) but it’s not inherently disordered.
When Xaos has succeeded in getting things seriously off track, the Angels may need to initiate change to bring human lives back into Order. This last is basically the category where the Thaumatarchy would put the Changes made by Theurges: empowered by Angels, necessary to battle Xaos, and thus part of Order. (And it would be the category for the sort of doctrine I think you intend to promote in reforming Xthonism.)
The Xthonic creation myth is a bit like our world’s Gnostic one, with Xaos playing a role somewhat like Ialdabaoth in a less populated (and much less gendered) version of the Apocryphon of John. The Ecclesiasts would definitely claim that Xthonos came first, not Chaos or change. But as Xthonos contemplates Its own Ordered perfection, Its thought generates various emanations, lesser levels of reality, like echoes or mirrors of Xthonos’s glory. Those emanations take aetherial form in the Angels, and then are manifested in the more flaw-prone matter of the rest of the known universe.
Xaos is the first emanation to become sufficiently flawed to cut itself off entirely from Xthonos and seek to create an independent “order” of filth, jealousy, and blasphemy on its level of creation. All rightly ordered beings, including the Angels, naturally oppose this unnatural violation.
Unlike the Gnostic myth, the official Xthonic one doesn’t attribute an actual divine spark to human souls; we are wrought by the Angels out of flaw-prone matter (fire and air, and aether for those in the know for our souls, plus a blend of all four for our bodies). Humans were designed to be the main proving-ground on which Xaos will be defeated and the glory of Xthonos confirmed. The reward for righteous humans is for our souls to be raised as close as we can ever come to Xthonos Itself–to Elysia, a realm of perfect matter, beyond the reach of flawed and bitter Xaos.
Yes, @idnlun and other skeptics are free to counter all this with a mass singalong of “Imagine.”
As the largest major cities near the war frontier, both Moncesano and Otsamor are kind of awful. Their main industry for centuries has been war; they’re heavily fortified, and thick with spies, soldiers, and speculators. You’re equally likely to be murdered by infiltrators or killed by your own side for being a suspected traitor.
If you did somehow manage to unite Empire and Hegemony (and let’s be clear, I’m not sure that’s a remotely thinkable ending), given the particularly intense mutual loathing between Erreziano and Halassurqs, you might do just as well with a capital in Aveche anyway–or Aegre in Shayard. The former Imperials wouldn’t consent to be ruled from Soretto (the current Erreziano capital), and nobody wants to live in Moncesano. Sea routes to Halassur are much faster than road travel along the isthmus anyway.
So do the Karagonds–but crop rotation only does so much when you’re doing other things that massively disrupt the soil ecology. Crop rotation still works fine for the yeomanry. But the big plantations are what feed the masses, and they’re needing incrementally more blood every year to get the same yields.
The thing with a wall, of course, is that if it doesn’t cover all sides, the outsiders can just walk, sail, or fly to the nearest gap…
All good speculations, by the way–not incoherent at all. And your “enormous gamble” will definitely be one road a rebellion can try to go down.
Ah, you’re talking about Chapter coughcoughcough.
It means that you have reduced the total anarchy in the realm. Congratulations! You have rebelled not only against the Hegemony, but against everyone’s expectation of what a rebel should be like.