Question: what are the extra deck?
Answer: The Extra Deck (Japanese: エクストラデッキ Ekusutora Dekki, abbreviated ＥＸ エクストラ デッキ in card text since Code of the Duelist), formerly known as the Fusion Deck ( 融 ゆう 合 ごう デッキ Yūgō Dekki), is a Deck where Fusion, Synchro, Xyz, and Link Monsters (as well as Pendulum Monsters that would otherwise have been sent from the field to ...