What happens if you play the game with your chosen champion shuffled in the deck?

According to the Tournament Rules, failing to separate your Chosen Champion and place it in the Champion Zone during the game setup is a deck legality/setup error.

The specific outcome depends on when the error is discovered and the tournament rules enforcement level (OPL):

• If caught before opening hands are drawn: A judge will restore the game state by allowing you to move the Chosen Champion from your Main Deck to the Champion Zone and then reshuffling your Main Deck (Rule 703.4.b.1).
• If caught after opening hands are drawn:
  • At casual or competitive OPL: The penalty is typically a [Warning]. A judge will attempt to restore the game state by moving your Chosen Champion to the Champion Zone if it is found in your hand or deck (Rule 703.4.b.3.a).
  • Penalty Upgrades: If the error is caught by an opponent rather than the erroring player, or if the deck cannot be restored to its correct state (e.g., you cannot find the Chosen Champion in your deck to move it to the zone), the penalty is upgraded to a [Game Loss] (Rule 703.4.b.3/4).
  • Exception: If you reach the point where you would move the Chosen Champion to the zone, but no copies are available in your Main Deck, the penalty may be downgraded to a [Warning] and gameplay can continue without you having a champion in the Champion Zone (Rule 703.4.b.4.a).

Important Note: Even if your Chosen Champion is shuffled into your Main Deck at the start of the game, it is still considered your Chosen Champion for game rules and effects, provided you properly registered it as such during deck construction. However, it must be in the Champion Zone to be played according to the rules for "Playing" (CR 419.1.a).