Comet Summoner (InstanceTopic, 18)
From Compile Worlds
Comet Summoner is an awesome spin-off of the Puyo and Madou Monogatari games. It features MitsukiWitch as she aspires to increase her magic power by going through a trial conducted in her dreams. The gameplay consists of grabbing stars and killing all of the enemies (all of them) in a room to progress to the next room, being able to summon devastating meteor attacks with the stars collected.
At the end of the game, Witch has to confront Dark Witch, an evil doppelgänger that possibly represents what Witch could be like if the power she is about to gain corrupts her. Dark Witch appears a few times throughout the game before the final conflict though, to taunt Witch a la Knuckles the Echidna.