Blood Hustler

The crime keyword folds a familiar aggressive impulse (target something an opponent controls) into a growth trigger, and the once-per-turn clamp is what keeps this from being a runaway. Any single targeted interaction you were already casting (a removal spell, a bounce, even a Duress-style discard aimed at an opponent's hand) gives it a counter, but stacking three crimes in a turn buys you nothing extra, so the design rewards a steady drip of interaction rather than an explosive turn built to inflate the body. That pacing is the point: it grows on tempo you were spending anyway, which means the counter accumulation is close to free in a deck already trading spells across the table. The activated ability is the fallback, converting flooded mana into a slow drain when the board stalls, and because it targets an opponent it can itself trip the crime trigger for a counter if you haven't already committed one that turn, though at four mana per point of life it is a closing valve, not an engine. The whole card sits at the intersection of a color's two long-standing hobbies (attrition and incremental life loss) and asks you to keep interacting to be rewarded, a Vampire Rogue built for players who treat targeting an opponent as a resource rather than a reaction.