Cabal Trainee

Defensive in a way that almost no other one-drop is: this thing exists to absorb attacks without ever blocking. Sacrifice it in response to a swing and the attacker loses two power until end of turn, which is enough to neuter a 2/X entirely or shrink a fattie enough that your blocker survives a fight it would otherwise lose. The -2/-0 line is the tell about what kind of card this is. It touches power only, so it cannot kill, cannot save a creature from a removal spell, and cannot break a board stall; its entire job is to take the bite out of one attack, once, and then leave the battlefield. The self-sacrifice clause is doing double duty as both cost and disposal: a 1/1 that converts itself into a single-creature damage-reduction spell is more efficient at the math than a Fog scaled down to one attacker, because the body could also have traded in combat first if the situation never came up. It reads as filler, and mostly it functions as filler, but the design is honest about its narrow purpose: a black creature that protects rather than threatens, priced so the protection costs you nothing but a card you were happy to spend.