So lets start with a player wanting a specific card for the deck he is building. Of course he could buy boosters to get cards, but as the cards in the booster packs are random, that could take a while. He could trade for the card he wants, but then he would have to give away his existing cards. And maybe some cards are "bind on pickup" and can't be traded. So to spend his points on the one card he wants, the player has to find the place where this card is sold. The search starts in a city. Having cities with a central function where people need to go back to is important for a world to feel alive. In this case cities have sages, which have books showing every single card in the game. Of course with some good user interface that lets you search, filter, and sort. Once he has found a card there, he clicks on it to ask the sage for information about where that card can be acquired. The sage answers by giving the player some general information, about what region (zone) the card is in. And so the voyage begins.