An extra theory for fun related to the core/demon crown...
Demon Crown controls frenzied Mimigas.. [the war]
Red Flower creates frenzied Mimigas... [many instances of this]
Core is connected to the Red Flower.... [killing the core turns frenzied mimigas back to normal...]
Does the Demon Crown control the Core? Or perhaps some kind of limited influence?
I mean how does one move the island around? Assuming that during the 10 year war, the island moved around... If the Core makes the island float [as is said repeatedly], then perhaps the Demon Crown has some control over making the island move.
Demon Crown does seem to make the user float.. perhaps there is some connection to the core...?
I mean why would Misery want the crown if she already had powerful magic? [assuming she inherited it from Jenka...] Control of the island would be a pretty huge and plausible reason for such a crown...
[Crown's are worn by rulers/leaders/kings/queens ... A floating magic kingdom (Zeal anyone?)...] (last scene Misery is next to the winged statue, looking out from the island... perhaps she doesn't want to leave; even after being cursed for so long..?)