What is commander damage?

Commander damage is a unique rule in the game of Magic: The Gathering that is specific to the Commander format. In this format, each player has a legendary creature designated as their commander, which begins the game in a separate zone called the command zone. Players can cast their commander from the command zone at any time by paying its mana cost.

When a player is dealt combat damage by an opponent's commander, that damage is referred to as commander damage. In the Commander format, if a player takes a total of 21 or more commander damage from a single opponent over the course of the game, that player loses the game.

Commander damage is a strategic element in the Commander format, as it creates an additional win condition that encourages players to be aware of their opponents' commanders and to protect themselves from taking too much damage. Players must be mindful of both dealing damage to their opponents and protecting themselves from commander damage in order to win the game.