I think he'll give us a fair chance to succeed if we work as a team and don't do anything stupid.
*look at the flaw I rolled*
I read that in a Wil Wheaton voice...
I didn't plan on this to be very much of a bad end game but things will progress naturally. One thing to note is that when I wrote that Lux bestowed her last pure ray of light on the lightbearer, it was both symbolical (choosing that person as her champion, and giving them her blessing) and literal. The endless twilight on the world, after darkness has prevailed? That's because there is still a ray of light left in the world. If the lightbearer dies or is corrupted by the forces of evil, the last ray of light is lost and night will descend. At which point the world is screwed and completely overrun by monsters in about 50 years. The adventurers may still continue their quest, just any resistance they put up will be worth little in the long run. So something like that would be the bad end. Now as for the "isolated heroine captured, brutalized, violated and enslaved* that's for when you do something stupid like break off from the main group and start doing stuff on your own.
This won't be one of the games where you lose all the fights. In fact, if you lose once and get away with it, you're lucky. The point of this game is to triumph heroically.
Basically tuckers02 got it right. The stakes are high and the odds against you because this is an epic story - a short campaign in which the fate of the world is at stake. It may seem overwhelming, but heroes in epics prevail against all that, do they not?
All that said, if your character falls and you'd like to have a bad end scenario... I'm not entirely against it