In order to get all five pieces of Exodia The Forbidden One, you must first save your game, then head to Grampa's shop, then challenge Yugi Motu to a duel. Bet a star card and then defeat Yugi. He isn't hard unless he uses Dark Magician. After you beat him if you are lucky you should get a piece of Exodia. Repeat until you have all 5 pieces, simple! Note: You have to be at level 137 to use Exodia so it may take a while before you can unleash its mighty wrath upon all who stand in your way.