Tetra Master is a Card based min-game in Final Fantasy IX. Once you have collected five cards you can begin challenging NPCs. To get this trophy you must Win against 100 unique NPCs. There are more than enough to accomplish this during the events that used to be disc 4 (on original PS). However if you challenge everyone in every area you travel to you will get this trophy in the Black Mage Village. Certain NPCs can be re challenged in the description means that unique NPCs can be challenged after major plot events. E.g. in Alexandria after returning from the Outer Continent.