Idk if this has been said, but what if instead of the mascot legendaries being the objective of the evil team(Skull or otherwise), but the Ultra Beasts? It would at least make sense for Aether to possibly be trying to obtain them, as with beings of such power they could "protect" pokemon right? Perhaps whoever is opposing the evil team will actually be trying to get the legendaries in hopes of being able to use their power to defeat the ultra beasts.