Unleash is a static ability from Return to Ravnica that has two effects. First, it lets you put an extra +1/+1 counter on a creature as it enters the battlefield — yay, bigger creatures! Second, it says that as long as the creature with unleash has one or more +1/+1 counters on it, it can’t block (boo).

Importantly, this second ability always applies, even if the creature wasn’t “unleashed” as it enters the battlefield. That means if another effect puts a +1/+1 counter on the creature with unleash after it enters the battlefield, that creature will be unable to block. You can even do this to your opponent’s creatures!

However, the timing of when you do this is important — you have to do it before you let your opponent actually declare blockers. Once blockers are declared, putting a +1/+1 counter on an unleash creature won’t remove it from combat. This is because the legality of a block is only checked in the instant that it’s actually made, and not afterwards. “Can’t block” means “Can’t be declared as a blocker as the declare blockers step begins”; it doesn’t mean “Can’t be a blocking creature in any way whatsoever.”

To give a concrete example, suppose you have a hefty Axebane Stag, but your opponent’s Thrill-Kill Assassin is threatening to deathtouch it if you ever attack. But, fortunately, you have Burst of Strength! You can target the Assassin with the Burst in order to make her stop blocking. But you must do this before the game enters the declare blockers step, at which point it would be much too late for you (and your Stag).

Conversely, if you have a Rakdos Cackler with no counters on it, you can block a 3/3 Beast token, then cast Common Bond to put 2 +1/+1 counters on it during the declare blockers step (after blockers have been declared). Now, even though your Cackler “can’t block”, that doesn’t matter because it’s already blocking. The creatures will trade when you move to the combat damage step.

Today’s Rules Tip written by Paul Baranay