Miig's explanation of where dreams are stored may seem vague because it is not a scientifically proven fact. The concept of dreams being stored in the marrow is a fictional idea that the author has created for the purposes of the story. It is a creative and imaginative interpretation of where dreams come from and how they are connected to a person's identity.
To put it simply, Miig believes that dreams are stored in the essence of a person, which is their marrow. Dreams are an essential part of a person's being and are intimately tied to their identity and sense of self. While this may not be a scientifically accurate explanation, it is a creative and unique idea that adds depth and richness to the story.