Maenad

The Myserious Maiden is a villain in Final Fantasy IV the After: Tsuki no Kikan. She looks a lot like the Summoner Rydia and shares her power to summon Eidolons. Her power as of yet seems unmatched, and she has yet to be defeated in even one of the many battles she has fought in. She can also use the powers of mind control to great effect. Kain? is her servent. The Maiden's mission is a repeat of Golbez's plan in the orginal Final Fantasy IV, to capture all eight Crystals though her true aim remains unknown.

Storyline
She first appears on the Red Moon where she is able to defeat both Golbez and Fusoya and resurrect Zeromus which destroys the Crystal Palace. She then goes down to Earth and attacks Baron, defeating the Red Wings with a swarm of monsters. Using the power of Bahamut, the Mysterious Maiden is able to beat King Cecil of Baron. Moving into the Feymarch, the Mysterious Maiden turns the entire Eidolon populace to stone, leaving Rydia unable to use her Summoner powers. Moving throughout the world, the Maiden is able to gather all eight Crystals, but also unifies the forces of good against her. They travel to the Moon to fight her.

With the final chapter not yet released, the Mysterious Maiden's fate remains unknown.