Complete the following levels to get the reward:

Unlockable     How to Unlock

Lightning     Obtain the Superstar Achievement.

Snow     Obtain the L’Cie paragon Achievement.

Sazh     Obtain the Loremaster Achievement.

Vanille     Obtain the Instrument of Faith Achievement.

Hope     Obtain the Instrument of Change Achievement.

Fang     Obtain the Treasure Hunter Achievement.

Serah     Obtain all Achievements.