Repentant Vampire

Most threshold rewards scale a number: a creature grows, a spell cheapens, an ability picks up a second mode once the graveyard hits seven. This one rewrites its allegiance instead. Cross the threshold and the Vampire turns white and gains a tap ability that destroys black creatures, a color flip that converts a generic black flier into a dedicated answer to its own kind. That swap is the whole conceit, and it is the rare threshold payoff that changes what the card is rather than how big it is. The design bites hardest in the matchups where black would otherwise have the least traction: against another black deck, a creature that mirrors the opponent's removal targets becomes the removal engine, without leaving the battlefield or asking for a second card.

Beneath that sits a slower clause on its own clock: deal combat damage to a creature, watch it die, grow. As an evasive body it can trade up in the air and bank counters over time, but that growth runs parallel to the transformation rather than feeding it. Threshold counts only what is in your own graveyard, while the creatures this kills land in the opponent's. The two halves are separate snowballs, not a loop. Locking the destruction ability behind transformation and restricting it to black is the discipline holding the card together: it is built to read as a liability early and turn into a weapon precisely when the game runs long.