The rule could be anything, as funny or as serious as you want. The universe will progress in a similar way that it has up until this point, unless your changed rule prevented it from doing so.
Some examples might be:
- The invention of currency is not allowed.
- Iron is slightly less stable.
- The Ancient Greeks are able to cultivate Silphium, which does not go extinct now.
Yeah but in this place nothingness creates energy… so like mini big bangs going off everywhere? Or we talking like zero point energy? Which opens up a bag of worms in our dimension where particles exist and don’t so they’re coming and going from somewhere, maybe this energy dimension lol.