I do have an idea, but I'm not sure how she can be integrated into the story. The character in question is this one I designed -> [url=http://fc05.deviantart.net/fs70/i/2013/096/c/c/social_reject_by_benit149-d60mw3b.jpg]HERE[/url]

Her name is Nil (yes, the image has her as Social Reject, but I changed it), a sort of emotionless Dark Knight-type girl who is only interested in 'devouring' negative emotions for sustenance, which there is plenty due to the girls battling each other. She can then use it to create dark energy weapons and project a field around her akin to the Somebody Else's Problem field from Hitchhiker's Galaxy. Heck, a lot of Nil's design and powers were based off of Touhou's Komeiji Koishi (the whole visible-yet-invisible phenomenon, at least). Thus, she could render herself 'invisible' to the magical girls and oversee them from afar. Only magical girls with extremely strong wills would be able to bypass this field, or if Nil allowed them to see her.

I wouldn't want to use her as part of a magical girl team due to her reclusive nature. Are there any suggestions you could think of with these ideas? A villainess? A government spy? An alien from afar? A mysterious benefactor? I'm not really sure what direction to take Nil in, but I would like to join this RP.