Tragic Banshee

The whole design hinges on the gap between its floor and its ceiling. Absent a death this turn, the morbid trigger nudges one opposing creature down by a single point of toughness, a rounding error that rarely kills anything worth killing. Cross the morbid threshold, though, and the same trigger becomes a -13/-13 blast that erases all but the largest threats. That conditional is the entire card: the black kill spell you want is stapled to a 5/3 body, but it only fires if a creature has already died before this Spirit arrives. That sequencing constraint is what pays for a five-mana removal-plus-beater package. You have to earn the big number, whether by trading in combat, chumping, or firing off a sacrifice effect earlier in the turn, and then follow with the Banshee to convert that death into a near-guaranteed kill. It rewards playing onto a developed, attrition-heavy board rather than into an empty one, turning an otherwise unremarkable body into a swing once the graveyard has been fed. The -13/-13 figure is deliberately excessive, and its size is doing real work: because -X/-X reduces toughness rather than dealing damage or destroying, it slides past indestructible entirely, dropping the creature to zero or less toughness and taking it as a state-based action. Protection from black is the notable dodge; toughness-boosting tricks and hexproof are the rest. The effect reads less like targeted removal and more like a guillotine you have to prime.