The Countdown Is at One

To play a Magic subgame, all players start a new game, using their libraries as their decks. No other cards, tokens, emblems, or anything else from the main game are included in the subgame.

If a player has fewer than seven cards in their main-game library, they’ll lose the subgame as it begins, regardless of how many mulligans that player takes.

If the subgame is a draw, no player won the subgame, so damage dealt to any player in the main game will be doubled.