Just to note that the card game isn't a collectable one quite like Magic etc. It uses fixed cards, covering weapons, items, traps, spells, armour, monsters and so on.
You deal a selection of each type of card onto the various "locations" and work your way through battling the monsters and aquiring (if you can) loot.
Your loot cards essentially become your "hp" - once you've used them all up you die. As such, the gameplay involves utilizing your cards (and re-using them) to best tackle the challenges presented.
Afer each mission, you refine your deck of cards based on what you've aquired during the mission, thus (if you survive), your character gets progressively stronger.
They have released a series of adventure pack add-ons which add more missions, and more powerful loot, to represent the characters levelling as they go. As you finish one expansion, you add the next to the box and so on. At a certain point, all the "basic" cards are removed, giving you a better chance of good rewards, at the expense of nastier enemies and traps.
It works pretty well, but as I say, really needs several players to bring the variety of an RPG party to life. 2 player is fun, but 3 or 4 is best. I'm not sure I'd play it solo.