On Disc Four, return to the card palace in Treno and enter. Like before, the bird guy will blow his horn and trigger a card game, but this time you'll be able to choose from ten different opponents to play. (The eleventh option closes the menu.) Each player has a small set of cards they always use; some of these cards can't be found anyhwere else. In particular, you'll want to get player 5's Flare card (which has a high attack power, but no defense), the three weapons from player 6, and all the Sacred Beast cards from player 7.