Return to Ravnica Booster Battle Pack
The Booster Battle Pack contains everything you need for a two-player game of Magic. When you open it up, you'll find two semi-randomized "decks" of 22 cards. Each one will be associated with one of the Return to Ravnica guilds.
You and your opponent decide which of you is playing which guild. Then you each open a Return to Ravnica booster (thoughtfully provided) and select up to five cards to add to your deck. You'll now each have a deck of up to 27 cards, and you can start playing immediately!