Rulings

For example, if you have 13 life, you'll lose 5 life.
If a player has 1 life, that player loses 1 life. If each player has 0 life after that, the game's a draw.
In a Two-Headed Giant game, each player loses a third of the team's life total rounded up. For example, if a team has 13 life, each player on that team loses 5 life and the team loses 10 life total.