Magic the gathering card question.?

Question

If i played a card that said 'in addition to play this card, sacrifice a creature and gain a card from your library'

would that mean i could sacrifice my opponents creature?

or is it just mine

Answer 1

Sadly, it means just your creatures.

501.6. Sacrifice

501.6a. To sacrifice a permanent, its controller moves it from the in-play zone directly to its owner’s graveyard. A player can’t sacrifice something that isn’t a permanent, or something that’s a permanent he or she doesn’t control. Sacrificing a permanent doesn’t destroy it, so regeneration or other effects that replace destruction can’t affect this action.

Answer 2

Unfortunately, you can’t sacrifice your opponent’s creatures. Sacrificing a creature is a drawback to a spell, and is often included in order to balance out the power level of the said spell. If one was allowed to sacrifice opponent’s creatures, then the spell would be way overpowered.

You also have to sacrifice a creature in order to play the spell, because it says so in the text of the spell. “As an additional cost, sacrifice…” Costs must be paid in Magic, else, you are shoplifting. In Magic, shoplifters are prosecuted to the full extent of the law.

I hope that helped.