Historical Rules · 1 February 2013
Rule 715.2
Official source text from the 1 February 2013 Rules release
As the subgame starts, an entirely new set of game zones is created. Each player takes all the cards in his or her main-game library, moves them to his or her subgame library, and shuffles them. No other cards in a main-game zone are moved to their corresponding subgame zone, except as specified in rules 715.2a-d. Randomly determine which player goes first. The subgame proceeds like a normal game, following all other rules in rule 103, "Starting the Game."