Well, Lucia and her companions from before unwittingly helped set the stage... they actually ventured into the demon realm themselves and did some stuff that SEEMED to hinder them, but played right into their hands. (Me and the other guy who helped with the sk'kirrim stuff had some... interestingly demonic politics going... ) The demons can get in just fine in small groups, which is why the sk'kirrim have been so necessary over the millennia... but to launch a full-scale assault would require a massive breach between the demon realm and the mortal realm.
Ahhh, the factions... that WOULD be a good idea.
First up, the old sk'kirrim government--
very church-centered, very hierarchial and run by those with a vested interest in staying in power. Remember that sk'kirrim live as long as Elves; most of the higher-ups were around when Lucia first showed up! They tended to have an attitude of superiority over the other races, since the sk'kirrim were the ones doing most of the demon-hunting, so they could have some... interesting motives here. They forcefully oppose Lucia and lay the blame for the current situation squarely on her, because in a major way she WAS their ruin. (Think fire and brimstone liberally applied to the sk'kirrim capital... yep, they HAD one. ) Most people don't like these guys too much. They want to be the ones in charge of countering the demons like they used to be, but Lucia claims they are unfit to and only make things worse. (No wonder they want her dead.)
Lucia's faction--
Lucia herself claims to be an agent of the god of this world (Skasthiir, aka the Sky Lord, who basically has the same sort of thing going as Iluvatar) and is simultaneously a harbinger of change and judgement. Her closest followers are known collectively as the Knights of Caladun, but everyone on her side has a strong belief that much of the sk'kirrim hierarchy has gone corrupt, and it is time to return to the old ways. They fight a war on three fronts-- they continue to fend off the demons as best they can while simultaneously fighting for their survival against others of their own kind and the other races that have turned on them. The Knights of Caladun believe it is absolutely essential to reconcile with the other races and work with them against the threat, instead of placing themselves as superior. Also, Lucia claims to have some sort of knowledge of things to come...
Soooo... basically, you could say that Lucia is the Rosyen of her age, at least, in the view of the majority of the population. (Whether she actually is or not remains to be seen... how many bad guys appear to be good guys at first? )
The sk'kirrim haters--
Pretty self-explanatory; like everyone else they acknowledge demonic threat as a reality but believe that the other races need to throw off the yoke of the sk'kirrim and make them obsolete altogether. They hate the two sk'kirrim factions equally and would quite like it if they all dropped dead. In fact, some of the more vigorous agitators among them believe that sk'kirrim might well be demons themselves and that removing them from the equation would make matters easier. They especially want Lucia dead.
Everyone Else--
Fighting amongst themselves about stupid things. As usual. (Plenty of wild cards out there...) And most things don't actually revolve around the sk'kirrim; they're just a major factor. (Trying to work stuff out! Heh.)