Board Thread:Questions and Answers/@comment-25921839-20180304014704/@comment-26181040-20180304015227

Probably bc the creators of both the Manga and Anime are unsure where the author is heading with Nigredo. Nigredo and Pestonya were involved in freeing some humans that were taken when Demiurge attacked Re-Estize. But that isn't explained until Vol 10 and Side Stories. So far she has a very minor role that the creators may have deemed insignificant. Plus the have a limited number of panels for Nigredo in the Manga and same also goes for the Anime.