A story like "The Apple" leaves me wondering if the small group of natives could possibly be the only ones on the planet. If not then were other villages living the same kind of existence with their own copies of Vaal? Was the relatively small amount of energy (in the rocks) really all there was to power Vaal? If so it seems rather dumb by whoever set up this whole thing.
This was a real case of leaving a lot of questions unanswered.