My new joke speculation. The succession story of Dawntrail will conclude about halfway or near 2/3's into the MSQ. Solution 9 will take up the last chunk.

That being said, the final boss is some Etheryis impression of a "v-tuber/holo-idol" gone completely bonkers and we have to destroy it to free the denizens of the place. You'll see it's likeness plastered all over the area. If anyone watched the Simpsons, it's sort of like that TreeHouse of horror where Flanders takes over the earth and brainwashed everyone.