Ghoulflesh

The -1/-1 is the part you'll notice first: a one-mana shrink that erases X/1s and quietly subtracts a point of toughness everywhere it lands. The stranger half is the type-line edit. Rewriting a creature into "a black Zombie in addition to its other colors and types" is a one-sided graft of identity onto something the opponent built around a different theme, and it only earns its keep in a deck whose own engine cares about that identity: tribal lords or anthem effects that key off Zombie, payoffs that reward you for the count of black creatures on the battlefield, mass effects that scale with a creature type rather than a body. Note which direction this actually runs: making an enemy creature black does not feed black's own removal (most of that targets nonblack), it shelters the thing instead. The recoloring is for your side of the ledger, not theirs. The contradiction that defines the card lives in its frame. It is an Aura, so it dies with its host and does nothing in the graveyard, yet the same -1/-1 can finish off the very creature whose new color and type you wanted to keep online. You need the body alive to harvest the tribal tag and dead to clear the lane, and those goals fight. That tension keeps it a setup piece in the lineage of identity-warping enchantments, the cards that edit what a creature is rather than whether it lives, never a clean answer.