In a Commander game, how much damage from a single commander results in an opponent losing the game?

In Commander format, a player loses the game if they have received 21 or more damage from a single commander throughout the course of the game. This rule specifically applies to the unique aspect of Commander where each player has a designated commander, and any damage that commander deals to a player counts towards that total.

The choice of 21 damage is significant as it creates a distinct threshold that players need to be aware of when strategizing their attacks and defenses. If an opponent receives 21 damage from a single commander's attacks, even if they have more life remaining, they lose the game immediately. This mechanic emphasizes the importance of the commander and adds a layer of strategy to both offense and defense in the game.

The other options do not reflect the correct threshold and do not align with the rules governing damage dealt by a commander. Therefore, the focus is squarely on the correct figure of 21, making it a key point of understanding in Commander format gameplay.