A Theme deck, previously known as a Preconstructed Theme Deck, is a playing deck of Pokemon Pokémon Trading Card game cards sold-pre packaged alongside mainstream card. Sets Most theme decks are designed with a specific (strategy such As Special) conditions or (theme such as Starter) pokemon pokémon. in mindost Theme decks are designed with a specific strategy (such as Special Conditions) or theme (such as starter Pokemon) pokémon in. mind