Once Upon a Midnight Dreary
Pandora has records about the Chains, but fantasy and reality of everything involved with the Abyss is so deeply interwoven that it's impossible to know what is truth, what is fiction, what is completely a lie. Lady Sharon smiles at him when he asks, a tilt to her head that says she's amused as much as she's also being helpful: "Would there be a better way to make people remember than through fairytales?"
Gilbert thinks of the heavy weight of Raven upon his mind, a oily, thick shadow in the place where his nightmares wait and he wonders if he should ask about Raven's tales.
He doesn't have to, in the end. Vincent reads the story out loud once, and Gilbert feels sick that he thinks that his brother chose to read it out loud just for him to listen, for him to know this. Gilbert doesn't understand Vincent and he doubts he ever will. Sometimes Vincent hums lullabies and he has never been able to decide if he knows the effect that causes or if he doesn't, so it's no surprise that he reads aloud, Gilbert thinks.
Once upon a time, there was a prince. The prince was loved by everyone, from the weak to the strong, for he was their champion. The prince would always fight for them, even if it meant he got hurt. No-one would ever doubt the prince's majesty, how much he would give for his people.
There was also a raven monster that ate hearts. He would send his ravens to attack townsfolk and then he would eat hearts, one after the other after the other.
But there was one heart that the Raven craved, and it was the heart of the prince, for it would be the purest heart of them all. So the monstrous Raven sent forth his minions and had them attack the prince's people. The prince's knight fell down first, unable to protect his lord. The people that the prince had wanted to protect so much all turning into ravens themselves, so that the prince was all alone there.
"Brother?" Vincent stops reading, smiles at him, and Gilbert tries not to shudder. He shouldn't fear his brother's smile, he knows. He shouldn't want to recoil from this. "I'm sorry, if I had known you were there, I'd have made it much more interesting. Do you care for the rest?"
"No, thank you," he finds himself saying, moving, going away. "I'm late already."
And he turns to walk away, feeling Vincent's eyes on his back.
Oz is the prince, of course. Golden, bright and laughing, so happy, the way Gilbert remembers him, green eyes and golden hair, and yes, he would be the beloved lord and Gilbert would kneel by his side, ready to protect him.
-- except that Oz is looking at him with horror and disgust and he doesn't know why, but Gilbert looks down at himself and he sees-- black feathers upon his arms, on his body, and he knows that Oz' heart is all that he needs, the prince's heart will help him and he's so hungry for it that--
He wakes up yelling, and he thinks he can hear Raven cawing with mirth inside him.
He can't find the book that Vincent was reading, and eventually he has to ask Elliot: a story about a prince with a pure heart and a monster that wanted to eat his heart.
"The Prince and the Raven?" Elliot rolls his eyes at him. "The author was crazy. All his books end up in tragedy."
"... do you know how that story ends?"
"That stupid thing?" Elliot hums, thoughtful, before he nods. "The Prince cuts his heart out with his own sword, so that the pieces of his heart chain the Raven forever. Stupid, isn't it? Instead of trying to kill hi-- Gilbert?"
Gilbert can feel Raven's claws against the chains in his brain. It caws, it caws, and the shadows inside him grow thick. Raven is laughing inside of him.
A knight that dies without being able to protect his master or a monster waiting for the moment where he can eat his lord's heart. A prince whose heart becomes chains.
Gilbert tells himself that he is neither, that he'll save Oz, he'll protect him this time, surely this time he won't fail, he will save Oz for sure.
Inside him, Raven waits.
The Fairytale, does, indeed, come from 'Princess Tutu', but since it's such a small part I didn't think it needed to be put as a crossover.