Burnt Offering
Instant
As an additional cost to cast this spell, sacrifice a creature.
Add X mana in any combination of and/or 
, where X is the sacrificed creature's mana value.
Rick O'Brien
Treasure Chest (PZ2)
• #65833Rulings
Players can only respond once this spell has been cast and all its costs have been paid. No one can try to destroy the creature you sacrificed to prevent you from casting this spell.
(wotc • 2013-04-15)
You must sacrifice exactly one creature to cast this spell; you cannot cast it without sacrificing a creature, and you cannot sacrifice additional creatures.
(wotc • 2013-04-15)
Rulings
Players can only respond once this spell has been cast and all its costs have been paid. No one can try to destroy the creature you sacrificed to prevent you from casting this spell.
(wotc • 2013-04-15)
You must sacrifice exactly one creature to cast this spell; you cannot cast it without sacrificing a creature, and you cannot sacrifice additional creatures.
(wotc • 2013-04-15)