Crookclaw Transmuter

Power/toughness switching is one of the older puzzle mechanics in the game, and this flash-flyer's job is to turn an opponent's stat line against itself in the window where it hurts most. The switch loves a low-toughness body, though not because it kills outright: flip a 5/1 attacker and it becomes a 1/5, defanging the swing while the creature lives. The lethal version of the trick is narrower and crueler. A creature whose original power is 0 inherits 0 toughness after the switch and dies to state-based action the instant the ability resolves, since SBAs are checked before any player gets priority. That makes the effect a clean answer to defensive bodies that wear all their stats in toughness, the high-wall blockers whose power column reads zero. The real removal angle, though, is marked damage. Switch a wounded creature so its new toughness sits below the damage already on it and it dies immediately, no waiting for cleanup, because the damage stays marked until the cleanup step while the switch takes effect now. Flash and flying make the body do double duty: it ambushes at instant speed without committing to the board first, then connects for evasive damage on the crackback. The reversibility is what bounds the effect: the switch lapses at end of turn, so it never permanently shrinks a threat, only opens a single window where the math betrays its owner.