But they couldn't stop a snowstorm. And the fact Celestia has lived over a thousand years and has probably learned every spell possible and said spell wasn't reminded to her during that crisis.
The said snow storm was powerful enough it needed an artifact dedicated to controlling and stopping it from overcasting the empire. I mean even Sombra ensured the thing was safe and in a location where it can still stop the storm just to show even Sombra didn't want to mess with it.
Which begs another question; if the Crystal Heart could be shattered so easily, you'd think it'd be ketp under a magic shield or something to protect when it's right outside where any accident could happen to it?
