PLEASE NOTE: The statistics in this article are incorrect. We will fix this and slap each other ASAP.
There are 8 different rarities in the game.
Common(C)- These are the most common cards. In a booster pack, you get 10 commons.
Uncommon(U)- These are, well, uncommon. In a booster pack, you will find 4 uncommons. There might be one extra every once in a while, giving you 5.
Rare(R)- You will find one of these in a booster pack. Every once in a while you might get an extra one, making there be 2.
Super Rare(S)- If you get some of these, it's cool enough to brag to your friends and family. You have a 62.5% to find one of these in your booster pack in addition to all the other cards.
Extra Uber Super Epic Supreme Rare(E)- This is just ridiculous. It's not even funny. You have a 15.625% chance of finding one of these added to your pack.
Exclusive(X)- These were made for a limited time, or were given out to certain people. These don't tend to come in the regular booster packs.
Unique(OMGLOLOLO)- These are one of a kind. They're so rare, you might even go as far as to call them VERY unique. Whatever the hell that means. These are usually obtained by winning tournaments, but we sometimes will slip these into an expansion pack for fun.
Other(N/A)- This means that the rarity isn't applicable. There isn't any use for this yet, but it will probably come up sometime.