When writing this sequence I considered a few pages of William trading blows with the horrors. However, I'd already written the sequence where William had trouble with just one horror. It didn't make sense for him to do so much better with 664 of them. William is faster, stronger, and tougher than a human being. The horrors are all faster, stronger, and tougher than him.
Still, he's fighting smart. Does anyone remember what happened the last time he pressed that button?