In 2HG, teams win and lose the game as a team, not as individuals. The most common way is for the team’s shared life total to go to 0, but there are other ways, such as one teammate running out of cards in his or her library; even if the other teammate can still draw cards, it’s a loss for the entire team.
The flip side of this, of course, is that if one teammate can’t lose the game, the entire team can’t lose the game. The classic example of this type of effect is Platinum Angel. If you control an Angel and your teammate doesn’t, you can’t lose the game for any in-game reason. Even if your teammate runs out of cards in his or her library, it can’t cause you to lose the game, so it can’t cause your teammate to lose the game, either! As long as you manage to keep the Angel alive, you and your teammate will be able to continue playing (albeit with one empty library).
Today’s Rules Tip written by Jen Wong