Board Thread:Speculation House/@comment-87.113.94.18-20130908174333/@comment-10390252-20130908184305

In the full-length Opening, it drops to the ground behind the girls and blows a hole in the ground. It's some kind of dark spell, possibly the power behind the Grimm trying to take them out before they can engage the Grimm around them. It's the biggest proof so far, IMHO, that the Grimm aren't just animals but have a higher intelligence behind them.

Fortunately, Ruby sees what it is and gets everyone out of the way before it detonates.