A king from a different land shows up and blackmails Rue. "I know you, Kraehe, and I'll tell everyone that you bewitched the prince... You know they'll believe it."

No, maybe a threat to hurt him will be better? He shows her what he can do, and won't, because it's fun the way he's doing it. So she thinks to buy time.

And he makes her stay away from Siegfried. He makes him jealous. He tries to make Siegfried give up, and in the end, he's able to provoke him into striking. He uses that to bewitch the crowd, or at least about this situation, and have him captured.

How it plays out: after Siegfried slaps him, he tells his own guards to deal with him. Then he reveals who he really means.

What about a macguffin? What if the Raven pecked something in particular from the people's hearts and hid it away?

Oh but then it could just not be the raven, but rather a remnant, or the "other ravens." Trying to get revenge by making him their prince. There's something eluding me here, an important point. Oh yeah, the solution. Siegfried addresses the people? Maybe it's an entire kingdom touched by the raven blood?

Wait, why raven stuff at all? Why not just have some of the people plotting this? His kingdom is his enemy? But how to solve it other than a cliche speech?

What if the raven's influence lingered right up until he died? And they think that the raven prince would at least lead them, at least accept their hearts? So he needs to find a way to purify them - and discovers he can do it by taking it into himself?

What if the raven knew what the prince didn't - an entrance to the story - and had his troops laying waste to the prince's home while he was gone? And told them that soon the prince would be able to accept their hearts, for he had taken in the blood?

Is this where a resurrected lohengrin comes in? Maybe he's the one who tries to "court" Rue?

It's perfect - more than it should be with the story ended. It still feels like a story and they both grow more and more uneasy without admitting it. This makes it easy for the prince to think that Rue might want to leave him, choosing someone more obviously perfect.

When an old friend turns out to be an old enemy, Siegfried finds that no one will trust him - one side wants him to give in, the other wants him to be pure.