When you're progressing in the campaign tree in Magic: The Gathering - Duels of the Planeswalkers 2013 on steam, and you're playing in the single player campaign, what increases your chances of unlocking better cards? Is it the particular campaign stage or is it entirely random based on the deck you're using?
The cards are unlocked in order, from the deck you're currently using. There is no random element. If your deck is fully unlocked, you won't unlock any cards. You can find the decklists and unlock lists here.