What happens when a player has 0 or less life?

When a player has 0 or less life, that player loses the game. This is a fundamental rule in Magic: The Gathering, and it applies uniformly regardless of the circumstances leading to the player's life total reaching this state. Losing all life effectively concludes that player's participation in the game.

Other choices are not applicable in this context. The game does not continue without penalty when a player's life total reaches zero, as that would deny the standard game outcome dictated by the rules. There is also no requirement to discard cards or draw cards simply based on a life total of 0 or less, as these actions pertain to other game mechanics and conditions. Thus, the clear and direct consequence of a player reaching 0 or less life is that they immediately lose the game.