Ravenous Harpy

A sacrifice outlet and a payoff stapled into one body, which is the design tension worth noting: most aristocrats engines split those jobs across two cards, asking you to assemble an outlet (a Carrion Feeder, a Viscera Seer) and something to reward the deaths. This Harpy collapses both into a single flyer, so every creature you feed it converts directly into evasive damage. The one-mana price on each sacrifice is the brake. Because the counters are not free, growth stays deliberate rather than explosive, and no single overloaded turn runs away with the game. The "another creature" clause is the other quiet restriction: it cannot eat itself to chump-block its way out of trouble, so the body it builds is the body that has to attack. This is a graveyard-agnostic sink that turns dying creatures into a clock, with flying handling the part where a small ground attacker would otherwise stall. The 1/2 frame is fragile on its own, which is the honest read: it needs fodder and time to matter, and it dies to almost anything before it gets going. But as a creature that wants other creatures to die anyway, it sits naturally alongside token-makers and recursion, where the supply of sacrifice material is already part of the plan.