User blog comment:ThatDisneyGeek/Tartarus Arc Changes/@comment-26287497-20150601013107/@comment-4999650-20150603003726

They never really explained the extent of this transformation. It was induced by Kyoka's Enhancement and later fortified with Hell's Core but both seem to be limited resources and related to Magic Barrier Particles (Kyoka's Curse + Hell's Core) so I pretty much deduced that whatever turned her Demon is out of her system and/or the Ethernano in their world just eventually purified her back into her normal form. Then again, Mira did say she had those particles in her, so perhaps Minerva can utilize her new form at will much like how Mira can?