Blind Obedience | Magic: The Gathering
Formats Blind Obedience is Legal in
Official Oracle Text for Blind Obedience
Artifacts and creatures your opponents control enter the battlefield tapped.
Official Rulings for Blind Obedience
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.