Xanxus , Flame of Lament

Flying, Ward- Discard a card
At the beginning of your end step ,you may
sacrifice a creature. If you do, choose one. If X is
13 or more, you may choose both instead:
• Xanxus deals X damage to each of up to
two targets.
• Xanxus deals half X damage ,rounded down ,to
each opponent and each planeswalker they control.
Each time, X is the total power of creatures you've sacrificed this turn.