Hungry Ghoul

The purest form of a sacrifice payoff: a body that eats your other creatures and grows one counter at a time, with no death trigger, no card draw, no drain bolted on. The mana cost per activation is what keeps it out of combo territory. Sacrifice outlets that are free (or that pay for themselves) are the ones that go infinite or bury an opponent in triggers; charging a mana per body converts the loop into a clock rather than an engine, so the reward is a growing threat and nothing more. That places it in a line of black creatures that turn dying bodies into permanent size, Carrion Feeder being the cleanest historical parallel: same principle of feeding one-drop fodder into a counter at a time, minus the can't-block clause. It wants a board that spits out expendable tokens or a graveyard-and-aristocrats shell where the creatures were headed to the yard anyway; absent that, it is a 2/2 with an ability it can rarely afford to fire. Where it does distinguish itself from a pump spell is that the counters are permanent state, not until-end-of-turn buffs, so the size can be built up across several turns instead of spent in one. That permanence has a ceiling, though: bounce it and the counters fall off with the creature, so the growth is durable against removal that trades on the battlefield, not against anything that sends it back to hand.