The remaining crystals are exclusive to the Talisdam, and are all obtained after beating each Kingdragon once in the overworld and again in a dungeon, via Quest Mode.
Talisdam Only Crystals: •Fire Legion Crystal •Tornado Legion Crystal •Earthquake Legion Crystal •Storm Legion Crystal •Necrom Legion Crystal •Spiritual Legion Crystal •Prince Crystal 2 (This crystal does nothing but act as a trophy. Proof you've completed the seventh quest.)