Knight of Obligation

Text:

Vigilance
Extort (Whenever you cast a spell, you may pay . If you do, each opponent loses 1 life and you gain that much life.)

Rulings:

• 4/15/2013 You may pay <img src="/Handlers/Image.ashx?size=small&amp;name=WB&amp;type=symbol" alt="White or Black" align="absbottom" /> a maximum of one time for each extort triggered ability. You decide whether to pay when the ability resolves.
• 4/15/2013 The amount of life you gain from extort is based on the total amount of life lost, not necessarily the number of opponents you have. For example, if your opponent’s life total can’t change (perhaps because that player controls Platinum Emperion), you won’t gain any life.
• 4/15/2013 The extort ability doesn’t target any player.