Jenova is the singular most evil abomination ever created. I cannot, however, reveal just how evil she is without spoiling more of the story than I already have. The first time you meet Jenova is in Shinra's Headquarters. All you see is a decapitated figure, before you are quickly caught by the Shinra and Hojo. From that point on, however, all hell breaks loose, in the form of Sephiroth. Your mission is permanently changed, and it is now to destroy the Mother of all Evil, and her malevolent and all-powerful spawn, Sephiroth.