In the Challenge Hall area of the game, you will find a special place where Challenge Cups are held. These Challenge Cups have you face off against three characters in a row, allowing for you to alter your deck and save between each match.
The first Challenge Cups are after you earn 3 and 5 medals, and always have you facing off against your rival, Ronald, at the final round. The prizes for these two challenge cups are always set.
However, after that, the Challenge Cup is not always open. Instead, whenever you load your save game up, there is a slim chance that the Challenge Cup will be open for entry again. This time, you won't necessarily face Ronald again, but he will appear from time to time as an opponent.
Upon every completion of the Challenge Cup, you will receive one of the many Promotional Cards, which allow for you to fully build a deck using them.