What would be ironic is if the whole way to "win" (like, win for reals as in fulfilling whatever nebulous requirements were set in place by the Mr. Tom guy and/or whatever GM powers exist) is if the fate of the world (or BT at least) depended on the actions of adventurers. Like...most fantasy media tends to portray. No, really, how often do you see nobles in their fancy silks going out searching for the Lost Legendary MacGuffin of Ultimate Deus ex Machina Ass Saving Humanity in the Eleventh Hour miscellany? Yeah, sure, sometimes it turns out the filthy commoner is a royal in disguise/unknown heir to the throne/a god incarnate/some important dude with amnesia/etc. But the point is he starts off and for the majority of the story, is considered a commoner, or some equivalent.
For reference, let's look at the following stuff:
1. The Pyridian Chronicles (Or whatever they're called. You know, the one with the pig that tells oracles, and there were five books. The hero was a pig farmer kid who defeated Arawn or something, and became the high king at the end. Anyway, for the most part, our hero was a pig farmer.
2. The Black Company. Well, technically they were mercenaries, but eh...
3. Lord of the Rings. Yeah, there's Aragorn, the king and all, but he gets introduced as a normal ranger dude. And in any case, even with the powerful wizard guy, the elf dude, the dwarf, etc, the guys who actually defeat Sauron and save the world are a bunch of hobbits from some little hobbit village, who are essentially little commoners, pun intended.
4. Legend of Zelda. For a game example, in all incarnations of our green-clad southpaw, he is a commoner, in whatever equivalent exists in Hyrule. I assume there is nobility, since there's this princess called Zelda (lol) and Link is definitely not part of that class at the beginning, though it seems as though lines aren't as clear since you can talk to her and she gives you quests and stuff. Well, actually, I'm not sure what Link is in Skyward Sword. But I do know in Twilight Princess he started off as a village boy.
5. Fable. Because, you know, it's a lolworthy game. Yeah, I know what happens in 3. But in 1 and 2, you start off as a commoner kid. Then you can grow to own the world, but still, that's a different matter.
My conclusion is that BT is meant to be saved by adventurers. The Invasion will be thwarted, if at all, by the efforts of commoners. If nobles are to play any role at all beyond that of stupid and ineffective, but infinitely arrogant and ignorant annoyances, it would be as human shields to slow down the tide of the daimons, thus buying time for the adventurers to use their Deus ex machina.
Disclaimer: However, it is not guaranteed that the DeM is in any way easy to use. It is far more likely that the game will conspire to have the advies fail because they are also played by human players who are generally pretty bad at working together for anything in this game. Well, especially true in situations like these. It is my belief that a bunch of dudes will find out how to win, but fail to tell anyone, and in that way, fail utterly because they are too dumb to realize that they cannot do it alone. That is also a point about humans: We place too much importance on ourselves. Alone we are nothing. Alone we are weak. A naked human is the most vulnerable animal that walks the earth. Too many people used to living in comfort forget that. Then again...Arrogance. Hubris. The venom that the gods detest and for which they punish humans who think to possess such qualities. So too is it the drug that demons use to seduce men unto their own destruction. Fun stuff yo.