Panic

Forbidding a block was never the hard part; the wrinkle here is the leash Wizards put on it. Panic can only be cast during combat before blockers are declared, which fences the effect inside a single phase: you cannot stockpile it for value, cannot fire it as a tempo play on a later turn, cannot do anything with it except during combat before defense gets to answer. Declare attackers, pin the chump or the wall, then watch blocks resolve with one fewer option for the defender. That narrow window is what pays for the cantrip stapled on. Spending your one red mana to push a single point of combat damage would be a bad trade in a vacuum, so the card hands a card back at the next upkeep to make the trade resource-neutral. The deferral is doing deliberate work, too: because the draw lands on the following turn rather than immediately, you never refill in time to spend the new card on this combat. Panic stays a pure attacking decision in the moment and only squares the ledger after the fact. This is early design splitting two favors (remove a blocker, replace itself) across one mana and then walling off the removal behind a phase restriction, so the combat-shaping half could never leak out of the step it was built to serve.