Metamorphosis | Magic: The Gathering
Formats Metamorphosis is Legal in
Official Oracle Text for Metamorphosis
Add X mana of any one color to your mana pool, where X is one plus the sacrificed creature's converted mana cost. Spend this mana only to cast creature spells.
Official Rulings for Metamorphosis
4/15/2013 : You must sacrifice exactly one creature to cast this spell; you cannot cast it without sacrificing a creature, and you cannot sacrifice additional creatures.
4/15/2013 : 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.