I think she’s trying to get rid of all the realms and destroy all the people in it. At least that’s what the promo said for the finale. But maybe she wants that so no one could jeopardize their family and it will be just them ruling the land.
I guess that is fine, but why keep calling it the final battle? Why doesn’t she just say that “The End” is coming? Calling it the final battle makes it seem like she isn’t sure that she is going to win, and I would expect her to be a bit more cocky. Also, which has she waited until now to release the dust? How did she get transfer it from the Dark Realm and why didn’t she just use it whilst she was there?