I don't think this should have a creepypasta tag. The idea that these entities are part of something bigger, and the exchanging of the pebbles and what they represent, all seem SCP-ish to me, like 089 (Moloch, so you don't have to go look it up and re-read it). I mean, "a deal was made." This seems like something dangerous that agreed to help contain something even more dangerous, but for a hefty price. However, I can understand the tag and won't mess with it.
All that said, this was a simple, creepy tale, and despite my hatred of human sacrifice (especially kids), I upvoted.