This question has come up a few times recently, because the answer doesn’t seem to make sense to everyone. What happens when you attack with a Wild Beastmaster and your opponent responds to the trigger by casting Downsize or Tragic Slip targeting the Beastmaster?

Well the first thing to realize is that the Beastmaster’s power is only checked as its triggered ability resolves.

The next thing to point out is that it is definitely possible for a creature to have negative power or toughness. While most numbers in Magic only use positive values or zero, a few things allow negative values to be used, including anything that: sets a player’s life total to a specific value, doubles a player’s life total, sets a creature’s power or toughness to a specific value, or otherwise modifies a creature’s power or toughness.

So, if the Beastmaster is a -3/1 creature when its triggered ability resolves because of Downsize, the ability will give +X/+X to each other creature. Since X = -3, you just use simple math to figure out that adding a negative is the same as subtracting. Therefore, +(-3)/+(-3) is the same as -3/-3. All your other creatures get -3/-3 when the ability resolves.

Consider now if Tragic Slip with Morbid was used instead! The Beastmaster becomes -12/-12 and dies, and the ability will resolve using last-known information about the Beastmaster as it last existed on the battlefield. All your other creatures get -12/-12 and almost certainly will be dead. That’s what we call “a blowout.”

Today’s Rules Tip written by
Josh Stansfield