Ah, I see. So everyone gets every card simply by participating? That makes more sense then.
Well, mostly. Unfortunately, to give a proper answer I need to explain how the game works. It's two players (could be against AI, which is very good) only, and every player gets 4 cards from each of 5 schools of magic. The 4 schools common for both players, and the 5th you choose when you start a game. In the first version you could not build a deck at all because devs argued that it makes the game unbalanced. It has an algorithm how the cards are dealt, which ensures that that no card can appear in both player's hand and that the relative power of the 4 cards in each school is about the same.
The devs DID add a deck builder in the latest expansion, but the game really gets weird if you start playing it with custom decks.
Now, when there was no expansion, everyone would get every card when they buy the game.
However expansions added additional non-main schools of magic. So if some-one with expansion plays against someonewithout, the 5th school choice will be limited for the one who does not have the expansion.
So far there were 3 expansions about a year apart.
