Pokemon Trading Card Game's first-ever expansion set is titled Mythical Island, which added a series of cards that can be collected by opening booster packs with adorable Mew-themed artwork on them. With the addition of Mythical Island, plenty of the newly-added cards became viable for use in deck-building, either as standalone Ace Pokemon or in synergy with cards from the same set or the previous set, Genetic Apex. As battling is an important part of the game that can be used to go up against other players or even earn rewards during limited-time events, building a series of strong decks gives players good versatility moving forward.