Originally posted by Don't take it puzzlingly, babe:The base game contains 10 decks and 2 free sealed slots, the expansion adds an additional 5 decks, but no sealed slots. The decks are unlocked by playing the single-player campaign, and additional cards for each deck are unlocked by winning games with that deck.The deck keys automatically unlock the deck in question and all the additional cards for it. In other words, they're just shortcuts. Please note that buying a deck key for an expansion deck won't do anything unless you also own the expansion.The foil conversions just make your cards shiny. This is an optional visual effect only. When playing online, other players will be able to see the foil effect on your cards, unless they have it turned off in their options menu.Sealed deck is a limited format where you get a set of 15-card booster packs and build a deck from scratch. Each sealed slot is effectively a different 'deck'. Whether or not buying the additional slots depends on how much you enjoy sealed mode. Since the game comes with 2 free slots, there's no point in considering buying the extra ones until you've already used both of those.In short, if you're interested in the game, you only need the base game and maybe the expansion.