There are multiple palyable characters in Hyrule Warriors aside from Link, including Midna and Zelda. In a live-stream session of the game, Nintendo’s product development group, Treehouse, provided an in-depth look at Link and Midna.
Late in the video, around the 28:00 mark, you get to see something particularly cool. You can get one of the Great Fairies in the game to summon the moon hovering over Termina in The Legend of Zelda: Majora’s Mask, and bring it down onto your enemy for some sort of assist attack.
Hyrule Warriors will be available this September in North America.