Historical Rules · 1 June 2020
Rule 720.2
Official source text from the 1 June 2020 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 720.2a–d. Randomly determine which player goes first. The subgame proceeds like a normal game, following all other rules in rule 103, “Starting the Game.”