Campaign of Vengeance
The five-mana price is the tell that this is a board-state amplifier, not a finisher in its own right. The drain fires on attack declaration, not on damage, so it pays out the moment a creature is turned sideways regardless of whether it connects, gets chump-blocked, or dies in combat. That detaches the payoff from the fragile part of combat: a token swarm that would otherwise trade down still bleeds the defender for one apiece, and the asymmetrical drain (they lose, you gain) widens the race before blockers are even assigned. The design rewards width over height, which puts it in the lineage of go-wide white-black drain effects where each individual attacker is worth almost nothing but the aggregate triggers compound fast. It deals no direct damage and answers nothing on the opponent's side; the reward is per-attacker and paid out across a board you have already invested in building. With no creatures of your own it does nothing, and behind a lone attacker it is barely a nudge. Pointed by a battlefield full of expendable bodies, it turns every attack step into something close to a Blood Artist trigger that needs nothing to die, and the life swing scales with exactly the kind of board the enchantment asks you to assemble.
