Historical Rules · 27 April 2018
Rule 719.2
Official source text from the 27 April 2018 Rules release
As the subgame starts, an entirely new set of game zones is created. Each player takes all the cards in their main-game library, moves them to their 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 719.2a–d. Randomly determine which player goes first. The subgame proceeds like a normal game, following all other rules in rule 103, “Starting the Game.”