Cragganwick Cremator

• WWizards of the Coast2020-08-07
  Official Ruling
  You choose the target player or planeswalker when the ability is put onto the stack. You won't know how much damage will be dealt until the ability resolves.
• WWizards of the Coast2020-08-07
  Official Ruling
  Cragganwick Cremator deals damage equal to the discarded creature card's power as it exists in your graveyard.
• WWizards of the Coast2020-08-07
  Official Ruling
  If you have no cards in hand when Cragganwick Cremator's ability resolves, you don't discard anything.
• WWizards of the Coast2020-08-07
  Official Ruling
  If the target player or planeswalker is an illegal target by the time the ability tries to resolve, the ability won't resolve. You won't discard a card.

Rulings via Scryfall