What is the correct start of game procedure in BO3 competitive 1v1, including when to select/reveal Battlefields, roll dice, and choose starting player?

Ruling: The start of game procedure follows a specific sequence where Battlefields are chosen hidden before being revealed simultaneously, and player order is determined by a random process that decides who gets to choose whether to go first or second.

Sequence:

• Reveal Legend
• Reveal Chosen Champion
• Choose hidden Battlefields (both players choose without knowing opponent's choice)
• Reveal chosen Battlefields (simultaneously)
• Shuffle decks
• Determine player order (mutually agreed upon random method decides who chooses whether to go first or second)
• Draw 4, mulligan (first player decides first)
• Start play

Nuances:

• The Battlefield process is split into two steps (choose hidden, then reveal) to ensure both players choose without knowing what the other has chosen
• The random process determines who gets to choose turn order, not who goes first directly