From Bulbapedia, the community-driven Pokémon encyclopedia.
Dee (Japanese: ディー) is one of the Ghost Masters located in the Sealed Fort, located on GR Island in Pokémon Card GB2: Here Comes Team GR! Dee can be found in the sixth of the nine statues in the main room. Players who defeat Dee will obtain a Present Pack, which can consist of any card that can be found in a booster pack in the game.
Big Thunder Deck
Big Thunder Deck (Japanese: ビッグサンダーデッキ) is the deck played by Dee. The deck consists of exactly three species of Pokémon, with two being exclusive to the two GBC games. The deck strategy is focused around Zapdos.