Ambush

Granting first strike only to blockers is the whole design statement here, and it is also the constraint that quietly disqualifies the card. The defending player gets to spring a trap: small bodies suddenly kill bigger attackers and live, which is exactly what first strike is built to do. But the effect can never initiate; it does nothing on your own attack, nothing on a turn where the opponent declines to swing into open mana. Four mana to hold up a contingent, blockers-only buff that does nothing about half the time is the rate problem in full. This sits at the crossing of two ideas Wizards was still calibrating in this era: instant-speed combat manipulation as a red specialty, and tricks that pay the defender for setting a trap rather than starting the fight. The defensive-only clause is the design discipline meant to balance a sweeping first-strike grant, but the price was set as if the effect were two-sided, and it is not. A cheaper piece of removal or a single well-placed creature closes the same window more reliably and without asking you to leave mana untapped through your opponent's whole combat. The granted keyword is correct flavor for an ambush; the cost is what kept it from ever earning a slot, and it reads now as a marker of how much tighter combat-trick math has become since.