10/4/2004: If you have multiple Lich cards on the battlefield, you must sacrifice a permanent for each damage done to you for each Lich. This is because the sacrifice is a triggered ability. But you only draw one card for each life gained regardless of how many Liches you have. This is because the draw is a replacement effect and not a triggered one. You lose if any one of the Liches leaves the battlefield.
10/4/2004: If you take more than one damage at a time, sacrifice the permanents for that damage simultaneously. This allows you to sacrifice both a creature and any Aura that is on it all at once.
10/4/2004: You can't pay life, just like any player at less than one life can't pay life. You can pay zero life if you want.
10/4/2004: The phrase "When Lich leaves the battlefield, you lose the game" is an absolute statement. Note that you will normally lose when Lich leaves the battlefield as a State-Based Action before you can take any actions because your life total is normally zero or less while you control Lich. If you have a positive life total or are otherwise prevented from losing due to a zero life total, this triggered ability will cause you to lose the game anyway.
10/4/2004: If an opponent steals control of Lich and no other effect prevents you from losing with a life total of zero, you will lose the game due to a zero life total as a State-Based Action before you can take any actions. The last sentence doesn't apply in this case since the Lich didn't leave the battlefield.
10/4/2004: If an opponent steals control of Lich, their life total does not change. The life total changes for a player only when it enters the battlefield under that player's control.
10/4/2004: You can lose life and take damage, and thereby have a negative life total, while Lich is on the battlefield.
Unlimited Edition
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