Pack's Favor

The trick a combat trick like this wants to pull is being free, and convoke is how it asks. A flat +3/+3 instant has always been priced around three mana because that is what the effect is worth in a vacuum; here the printed cost can collapse to a single green pip or evaporate entirely, paid by the same creatures already committed to the board. That inverts the usual tension of a pump spell, which normally trades a card and a chunk of mana for a swing you have to hold up. Convoke lets a go-wide deck spend its width instead of its mana: the tokens that were going to attack anyway tap to push one of their number through a blocker, and you have spent nothing you needed. The cost it does carry is timing. Tapping creatures to cast it during your own combat means they cannot also attack, so the real decision is whether the +3/+3 on one body beats the damage you give up by sitting the rest down, or whether you cast it on the defensive turn when their attacks are already spent. That choice is the entire skill of the card, and it is a sharper one than the static rate suggests.