Instructions
Fight in the Duel Colosseum and defeat characters in order to obtain items. You will need to battle characters level 90 or above to get the items you are looking for.
Collect 1 Grand Slam, 5 Fayth's Dreams, and 5 Guts Orbs. These are all randomly dropped items that you will get by following Step 1.
Trade the 11 items above in to the Gil Shop to create the World Champion. Tidus is the only character who is able to equip this exclusive weapon.