We all know the Sixth Umbral Calamity was a great flood that emerged as a consequence of the War of the Magi between Mhach and Amdapor.

So I thought about what might have happened to the respective reflection to have tilted it hard enough in the direction of water to allow for a Rejoining.

Then it hit me: Blitzball!

Think about it - Blitzball in FFX was a worldwide phenomenon, everybody loved Blitzball. What does Blitzball require? That's right, an arena full of water.

So what if the Ascians convinced the inhabitants of whichever reflection they sought to rejoin to transform their entire world into a giant Blitzball arena?

I hope that's not the case, because I want one of the remaining reflections to be the Blitzball world, but unfortunately I think it would have been the smartest for the Ascians to use such a world for a rejoining. Maybe the Ascians actually invented Blitzball for their own twisted purposes...