There's a point in every writer's career when they get struck like a bolt of lightning, when their muse doesn't whisper... she shrieks, and she isn't going to leave you be until you hear her.
It might be a seed of an idea suddenly sprouts... but it's an oak tree on steroids, not the beanstalk you were expecting. It could be something you've been playing with for a while that suddenly explodes into a massive storyline, or a plot hole you couldn't plug, that suddenly resolves itself.
Whatever the result, it's undeniably overpowering. I've been hit with it numerous times, and today was one of them. I've been toying with ideas for a while now, and finally got one last night... but it wasn't more than a bare sketch, a brief outline that gave me some compelling characters to work with.
Well, now the thing has become a behemoth of mental gymnastics. Well, for the characters, at least. There's a plot twist or two that will be fun for the reader, methinks. And these characters are going to be truly, truly fun.
This year's NaNo is going to write itself, I swear. Gah. Now I have to wait for November 1st...
Ah well. I have a bunch of worldbuilding to do between now and then. Heck, I have to design a whole religion! The only thing I know about it is that it has a central Church (where the main character starts out) and that it is headed by a Pope-like figure, and that there is no distinction made between male and female priests (no priestesses).