Welcome to the Cave. See a card here you want? Want it so bad that you'd just be willing to take it? You can't! Bummer. However, if you give the Cave something in return it may give you the card, but then again, it may not. Oh well, trying never hurt anyone.
You can only attempt a trade one time per week.
The Cave hates having two or more or the same card/set. (This means that if you want to trade in a Trapped-09 and there is already a Trapped-07 in the pile of cards, you can't trade in your Trapped-09.)
