Did the failed ascension ritual allow the Xer'sai into runeterra more specifically Shurima.
Not the most mind blowing theory but I do think the failed ascension ritual allow the Xer'sai into Shurima. We know Azir does not know the existence of the Xer'sai so we can infer that The Xer'sai invaded Shurima after its downfall and destruction because the failed ritual. But why do I think specifically the failed ritual allowed the Xer'sai in and not some other random occurrence.
Well its hard to open the gap between universes know as the void that would most likely need a lot of energy what happened at the failed ascension ritual it cause a huge outburst of energy killing almost everything in its path. Would this be enough energy to weaken the threshold between worlds I think it would.
My other evidence Taunts specifically to Rek'sai no other void borns from Illaoi "Ugly thing. You weren't designed by gods you were made by fools." Why is this important well it becomes more obvious what she thinks of ascendants "You wanted to be a god! Instead, you are a useless antique!" and "Your soul is a fetid, stagnant pool untouched by the tide!" etc. We can see she doesn't think highly of most ascendants she would probably refer to them as fools. Although, how would she know the Xer'sai was brought into the world by ascendants? To be honest I don't have real solid proof other than her god is ancient and would know I guess? Sorry for the weak end What do you Think of this theory?