What is the penalty if a player starts a game with their chosen champion in their deck instead of in the command zone?

Ruling: If the erroring player calls a judge on themselves, they receive a warning and a judge retrieves the chosen champion regardless of when in the game it's discovered. If anyone else calls the judge after opening hands have been drawn, the erroring player receives a game loss.

Sequence:

• If discovered before opening hands are drawn: Find the chosen champion and give the erroring player a warning
• If discovered after opening hands are drawn and the erroring player calls the judge: Give a warning and retrieve the chosen champion
• If discovered after opening hands are drawn and anyone else calls the judge: The erroring player receives a game loss

Nuances:

• The timing of when the error is discovered (before or after opening hands) matters for the remedy
• Who notices and calls the judge determines whether it's a warning or game loss after opening hands are drawn
• The harsher penalty when someone else notices is intended to incentivize players to own up to mistakes and prevent strategic abuse (such as waiting for an opportune moment to claim a sideboard error)
• This same framework applies to sideboarding errors where players forget to desideboard