Board Thread:Questions and Answers/@comment-25921839-20180304014704

After knowing about Nigredo, the elder sister of Albedo and another younger sister of Albedo, I was quite amused by the fact that, none of them appeared in Manga and Anime. Why?

By the wiki, Nigredo is less evil but her face is horrible and she is a reasonable person. Than why is she kept in the prison and what wrong she has done to be put in a prison. 