Skinsling the Blasphemer

{2}{r}: Switch target creature's power and target creature's toughness until end of turn. This
ability costs {1}{b} more to activate if it targets
two creatures controlled by different players.
Whenever Skinsling, the Blasphemer deals
combat damage to a player, note that amount
for that player if it hasn't been noted for that
player. If the total of all numbers noted for that
player is exactly 13, that player loses the game.