>>125101818While a possibility, even if that's the ending we get it'll still be leagues better than Star just by the stuff already been introduced.
Star's finale was terrible not just cause of the concept itself, but the way it was executed. For starters, we have seen creatures of magic can still exist in a world without it with Vee so already the "Star killed millions" situation is somewhat lessened.
And unlike the sloppy job of Star, the "fusing the reals" situation already can be a plausible route without feeling like nothing in the show mattered.
In Star, the use of said concept was sloppy cause at the end of things, Toffee was 100% right. While in here, while Belos may want to fuse the two realms, we have already seen his methods of oppressing the people of the boiling isles signal us that his methods are tools are misguided, meaning that if Luz were to utilize said trope it would be in a way where it benefits everyone but him.
TL;DR, I don't want a repeat of Str's ending, but even if we do, TOH has already set enough points on its way to at leat make it feel plauivle, unlike Star where it really feels half-assed and not really thought out.
