Bloodcurdler

The upkeep mill makes this flier its own enabler: every turn it ticks one card closer to seven, after which it grows and starts feeding on the graveyard it spent the early game building. That self-correcting loop is the design tension worth noticing. The end-step exile of two cards claws back at the very total that turned the creature on, so a live Bloodcurdler is constantly threatening to undo its own threshold count unless other sources are stocking the yard faster than it drains it. It is a graveyard engine that punishes a deck leaning on this single body to cross the line and rewards a shell overfilling the yard from a dozen angles. The flying matters because the payoff ceiling is so modest (a 2/2 evasive beater is all the buff delivers) that the card earns its keep as connective tissue rather than as a threat: a slow drip toward threshold, a recurring exile to fuel effects that want cards leaving the graveyard, a clock that doubles as a graveyard valve. Most threshold enablers of the era were passive (a fetchland crack, a flashback cast, a card pitched to discard); this one asks you to accept ongoing graveyard attrition as the price of evasion and self-mill, which is a narrower bargain than it looks and a more honest one than most.