There is very little about Thrane that I like from Eberron in print. The idea of a para-Christian nation, but OMG, so scary, because Christians = Inquisitions and Crusades and intolerance, OMG again, is not only stupid and boring as a campaign element, but it's also extremely offensive to me. Not only that, you've mostly been lied to about the Crusades and the Inquisition both, and few people actually understand the reality of them; what they understand is a dishonest narrative told from the perspective of people who see it as leverage to attack Christianity. If you thought Fake News was a big deal, wait until you get a load of Fake Science and Fake History, as they say. But that's neither here nor there for purposes of this remixing project other than to say that the entire premise of Thrane needs to change significantly for it to be a place that has any interest for me.
However, there is at least one element of the backstory to the nation that I think makes sense; the idea that some kind of great evil is trapped in Flamekeep. A being that would be equivalent to Cthulhu, basically, yet associated with undeath and mutation is what is trapped here, comatose and sealed behind mystical chains in a dark pit with a fortress/cathedral built on top of it. This being is known colloquially as a the Sleeping One (but older and more formal texts give him the name of Tarush. This probably is not actually his "name" but an older title or sobriquet) Along with him are trapped some of his most loyal and twisted servants, including the Primordial Beasts and the Primordial Vampires. These being are to regular werewolves and vampires as grizzly bears are to chihuahuas. However, they remain sealed with their profane patron, although not as deeply and not as tightly. In fact, these primordials were knights of a religious order who heroically sacrificed themselves to keep Tarush sealed and asleep, but have been corrupted and twisted; turned into insane monsters, as the price for their heroism. Their order of Templars now rule openly in Thrane, and the temperament of the nation is as one under siege, who's primary purpose is to keep this unholy blasphemy contained at all cost. The entire nation, therefore, has developed a kind of militaristic, Spartan personality. However, they are not terribly interested in conquering the other nations for its own sake, although some of the more extreme see the very existence of the other nations, with their misplaced priorities, as a threat to the mission of the Templars. In fact, this wing is exactly the one that has turned the King (not Queen Diani; but King Dion) into a figurehead while they rule openly. The Council of Cardinals is the Council of Marshals, as befitting the more militaristic Templar organization that replaces what's in print. And the Keeper certainly isn't an eleven year old girl (?! lolwut, Keith Baker) named Jaela, but a middle-aged man named Jael, and he's more like a military commander than some kind of Delphic Oracle. Although I am fine with the idea of him being a much more moderating voice against the more aggressive Marshals.
Flamekeep itself will be seen very differently too. Because of the blasphemous presence of Tarush, it suffers from the astronomical improbability of always being night to a radius of about five miles from the center of the Cathedral where Tarush is sealed. The moon overhead has had its markings change, again very astronomically implausibly, to where it looks like the man in the moon is a skull face. It is also a magnet of sorts for evil creatures, if they can make it to the city through the thoroughly militarized zone around the city, and there are a number of much weaker creatures—usually minor undead and servitor daemons or imps—who leak out of the seals. They remain potent enough to keep the more powerful creatures contained, especially Tarush himself, but the fact that the smaller, sneakier monsters are able to slip out is worrisome to the Temple. That has only been happening since the end of the Last War.
These worries, as well as political manuevering within the Council of Marshalls, against the Keeper, from the rightful king, make Thrane a rather tense place to visit, but one that is desperately in need of heroes, certainly. I also see the idea of heroes of Thranish origin wandering the world looking for escaped monsters to slay, or other problems related to their misson to contain the Sleeping One as being relatively common. Fantasy Solomon Kanes, if you will. Relatively common, of course.
As an aside, when I say that the Sleeping One is buried under a seal and mystical chains, I don't mean to imply that he's physically in a pit in Flamekeep with gigantic chains locking him up. There is a pit, covered with a stone lid, and wrapped in magically forged chains, but the real home of the Sleeping One is in another dimension, and Flamekeep is merely a portal whereby he could potentially come into the world of Eberron. This is also why the smaller evils can occasionally slip through, and appear shockingly in the streets of Flamekeep. They don't have to come through the stone chained lid per se, because the sealing is more magical and symbolic than physical.
Thrane population Remixed:
Humans: 88%
Seraphim: 5%
Jann: 3%
Other: 4%