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Yes, it's the monster-sized raven created by Drosselmeyer that shattered Myutho's heart in the "story". He has the abillity to eat people's "hearts".
He needs the hearts of many people in order to gain back his full form. He kidnapped Rue Kuroha from her real parents to raise her as his daughter and giving her the powers to become Princess Kraehe, whom is also part of a heinously dark agenda. He was mentioned in the manga, but he's absent from it.