Collect eight crystal fragments of the indicated color to unlock the corresponding sub-character.

Aerith from Final Fantasy 7: Pink.
Ashe from Final Fantasy 12: Crimson.
Cid from Final Fantasy 3: Yellow.
Cosmos Final Fantasy Dissidia: Rainbow.
Faris from Final Fantasy 5: Red.
Kain from Final Fantasy 4: Navy Blue.
Locke from Final Fantasy 6: Blue.
Minwu from Final Fantasy 2: Silver.
Princess Sarah from Final Fantasy: Gold.
Prish from Final Fantasy 11: Purple.
Rydia from Final Fantasy 4: Emerald.
Seifer from Final Fantasy 8: Grey.
Sephiroth from Final Fantasy 7: Black.
Snow from Final Fantasy 13: White.
Vivi from Final Fantasy 9: Orange.
Yuuna from Final Fantasy 10: Sapphire.