Great job, CWR!
I appreciate you including the Big Secret, as I'm always annoyed by reviews that keep them from potential GMs. (But then, I'm even <u>more</u> annoyed by <u>games</u> that keep the Big Secret from the GM.
) And I agree with Praetorian that the Big Secret in this case seems rather limiting.
<spoiler>Is the explanation for the White Event as understood by the characters in the setting something that people cooked up after the fact to explain it? And if so, who came up with it?</spoiler>
Speaking of spoilers, you might want to consider using spoiler text for Big Secrets.
Regarding the mechanics: since attributes are on a 1-8 scale and skills are on a 0-5 scale, doesn't the system strongly bias in favor of attributes? Or does the partial success issue balance that out?