Phyrexian Boon

The split between +2/+1 and -1/-2 is the entire design, and it is a color-pie statement Alliances liked to make literal: black rewards its own and punishes everything else, encoded in the rules text rather than the flavor. On your own black creature it is a clean stat boost; on an opponent's nonblack creature it shrinks the body enough to kill the small ones outright and weaken the larger. The practical consequence is that its value swings hard on the color of the target. Against a black mirror it is dead as removal but still a serviceable buff; against the rest of the wheel it answers a creature at the cost of a three-mana Aura. That investment is the friction. Without flash, it commits at sorcery speed, so there is no holding it open as a surprise during combat. When it kills its target by dropping toughness to zero, the Aura goes to the graveyard with it: a one-for-one, since you spend a card to remove a card. When it merely shrinks a larger creature, you are left with an Aura strapped to something you do not control, where a bounce or sacrifice outlet on their side strands you. Designs that gate an effect on a target's color have stayed rare, making this an early and unusually committed example of the idea, built when black's identity was still drawn in sharp, punitive lines.