Two-Headed Giant is a fun multiplayer format where two-player teams battle against one another. Each team takes actions as a team rather than individually. There are some rules for Two-Headed Giant that differ from other multiplayer formats:
A teams loses when their life total is 0 or less, when they accumulate fifteen or more poison counters, or when either team member is unable to draw a card from their deck. Damage and loss of life happens to individual players, and the effects are applied to the team’s shared life total. The same is true of gaining life. For example, if one player gains life, the team’s life total goes up, but only one player’s “whenever you gain life” effect triggers.
Effects that read “each opponent” or “each player” affect each team member separately. For example, when Rabid Bloodsucker enters the battlefield, each player would lose 2 life—meaning each team loses 4 total life.