User blog comment:FairyRaven/Fairy Tail Chapter 363: The Stories That Demons Read, Review and Commentary/@comment-5840892-20131206153704/@comment-4829046-20131206181504

Well obviously, they are the sole reason for the "Darkness" =P None of the other characters were introduced for such an effect and thus didn't need any back-stories other than "Princess of an Alien Planet" and "Girl with a Japanese background". Hmm.... then again, I liked Kotegawa's sort-of-back-story but that's just cause she is one of my more favoured characters.