I was thinking about a possibility right now. Just like Baam has Leviathan inside him, could Traumerei also have some sort of Shinheuh inside him? It might be a bit reaching, but those green tendrils that appeared as soon as he summoned his Shinwonryuu look kinda similar to the projection of part of Levi's body when Baam attacks. Both look slightly transparent and both seem to have some sort of visible scales to me.
