MArcomage

After some thought over a long time period... I would recommend Collapse to be a rare, for the huge effect the card has on the game.

As in, the card is to represent a catastrophic event, right? They don't happen every other week. The card rarity should be in sync with the card's fluff.

you may be right, the damage is not big deal, but the possible stock reduction could be significant for zero cost card, and used in zero cost decks, the reduction of your own stock doesnt matter so much... but well its just concept, probably it wont be implemented and if so, it will be changed, so im leaving this and every other concept as open idea :)