@feha: Same evil (former) King, as before. He survived, because Noche didn't even care enough to make sure he actually was in that castle, when he slaughtered everyone.
Woooow. Viola's actions set new standards for bad judgment. As proud as the are of their little sister, doesn't she realize, that her siblings are people, who are willing to take their good friend's (demon king Noche) life, when he turns dangerous, to ensure the worlds survival? And that won't be even his own fault. Her acts of treachary on the other hand are voluntary. Siblings or not, they will have her head for this. Making the 13 most powerful people on their world, that can teleport everywhere, your enemy is daring.
My guess is her plan involves NOT getting associated with that king. You know, that king, that is so full of himself, that he will spill the beans at the next possible opportunity. I don't see how this can possible go wrong. I guess her scheme includes killing him of before he's able to. If she fucks up the timing, it's world ending time. But 0 is seemingly the number of f*cks she gives, if she can't be with Noche.
@aFFi: Sadly, that is true. The story took a nosedive, at that the time you pinpointed, for the reasons you listed.