The Mirage Arena has a new, humongous boss to battle in Kingdom Hearts: Birth by Sleep Final Mix. Players can team up to fight Monstro, the giant whale from Pinocchio. What makes this fight interesting is it takes place outside and inside Monstro. Every three minutes Monstro swallows the party whole. The whale’s digestive system has HP sapping stomach acid and Unversed to fight.
Another Mirage Arena feature is an ability called "Illusion L." This transforms your character into an Unversed, specifically a launching plant. Players inherit the attacks and parameters of the Unversed after metamorphosis.
Other features announced in Famitsu are a command board for Peter Pan and additional songs for the Rhythmic Ice Cream mini-game.
Kingdom Hearts: Birth by Sleep Final Mix comes out in Japan in January 2011.