Well based on BJH and Vanir's thoughts, I'd go out on a limb and say that it was Hermione's unborn baby that did the final deed to protect itself from imminent danger. The question then becomes who's baby is it to be this powerful at this stage?
Other than that, you have to start bringing in outside players to the scene if anybody else is involved.
Chris
Author's response
/Dayum/, you guys are good. I don't want to post any spoilers here but I will say there will be no "surprise" characters coming in at the last minute. In my first outline I had Kreature respond to Ginny's death with explosive force, but then changed my mind.
I'm allowed to do that.
It's my prerogative, right?
GG