Man, we literally see an Outer God descending in her ending. The same Outer God to whom her entire culture had been devoted from the inception. We literally hear her proclaming that she's delivering the world to said Outer God. Not even touching on Ranni's character or track record here. Just, we're directly shown what she wants to do, almost as directly as we've been shown that the world dies with the First Flame. I swear "Ranni wants to remove the interference of outer beings" is a level of delusion that can only be explained by simping.
And, well, besides the whole lightshow at the end, she is literally a puppet, in an example of FROM's typical level of subtlety.