Whipstitched Zombie

A standard 2/2 for two mana, with one string attached: it costs black mana every upkeep just to stay on the battlefield. The design idea is not a discounted body (the stats are exactly on rate) but a creature that taxes you for keeping it, a recurring friction that compounds as the game grinds out. That math is the interesting part, because it ages backwards from most cards: the upkeep payment is trivial when your mana is open and your hand is empty, and it bites hardest once that single black pip is competing with everything else you want to cast and your board has stalled into a standoff. The clause is a localized version of the upkeep-sacrifice lever black has reached for repeatedly, a relative of cumulative upkeep and echo, scoped down to one colored payment with no colorless attached. What it really asks of a deck is liquidity: black mana you are not otherwise spending, which quietly nudges it toward mono-black builds where the tax rounds to nothing rather than a real tradeoff. Strip the upkeep line and you have a vanilla 2/2 priced exactly at curve; the recurring payment is the entire reason the card exists, a deliberate piece of friction rather than a downside bolted onto an undercosted threat.