During development, we learned that the black chocobo was a favorite of Nomura's as it was the fastest chocobo in the original FINAL FANTASY VII minigame
Each ink (Amber, Amethyst, Emerald, Ruby, Sapphire, and Steel) enhances different parts of a characters personality, powers, and appearance, making for some truly unique gameplay
On each player's turn they ready any cards that are exerted (turned sideways) and then draw a card
If you mean 'challenging' other characters, or glimmers, in play Steel and Ruby are good at challenging and can get benefits for banishing opposing characters during challenges
What makes these cards so rare is that they were never meant to find their way into players hands
In The First Chapter we saw a giant Tinker Bell, Hades as a god on Olympus and Stitch performing live as a rock star