Makeshift Mauler

• WWizards of the Coast2013-04-15
  Official Ruling
  You must exile exactly one creature card from your graveyard to cast this spell; you cannot cast it without exiling a creature card, and you cannot exile additional creature cards.
• WWizards of the Coast2013-04-15
  Official Ruling
  Players can only respond once this spell has been cast and all its costs have been paid. No one can try to otherwise remove the creature card you exiled in order to prevent you from casting this spell.

Rulings via Scryfall