Collateral Damage

The whole transaction here is a discount paid in bodies. Bare three-damage burn at one red mana would be priced well above this; sacrificing a creature as an additional cost is what buys the rate down. That requirement is also the angle: this is not removal you reach for to answer a threat, because spending a creature to point three damage somewhere usually leaves you down on the board. It is burn for decks that are already throwing creatures away on purpose. The sacrifice clause converts a token, a spent attacker, or a creature carrying a death trigger into reach, and it does so at instant speed. The useful timing window is narrow because the sacrifice is an additional cost, not a choice made on resolution: you can respond to a removal spell by cashing the doomed creature in first, or fire it after blocks are declared but before combat damage, sacrificing an attacker that has already committed a blocker. Once combat damage has been dealt and the creature is gone, the window has closed; there is no chump-blocker left to feed the spell. Outside a deck built to supply it, the line reads as strictly worse than a vanilla burn spell, and that is the deliberate cost of admission: the effect only pays off when the creature you sacrifice was already a sunk cost.