Merfolk Trickster

A flash blocker that ambushes a creature is old hat; this one does something stranger. The tap is the lesser half: pinning an attacker or a would-be blocker is useful, but the loss-of-all-abilities clause is where the card bites. Flashed in during combat or in response to an activation, it switches off a creature's keywords, its tap abilities, even the static text holding a board together. A menacing threat stops evading blocks; an indestructible blocker stops being indestructible; a creature whose ability was midway up the stack still resolves, but the body that produced it goes inert for the turn. The 2/2 body matters less than the window: held up at instant speed, this is a permission-style answer living in the creature slot, sidestepping the sorcery-speed vulnerability that plagues most disruption of this shape. What holds the card in check is scope. The shutoff wears off at cleanup and reaches a single creature an opponent controls, so it disrupts a moment rather than neutralizing a permanent: it punishes a play, it does not erase a threat. Tempo decks built around interaction-on-a-stick (deploying a relevant body and a counterspell-adjacent effect in the same card) have long wanted a creature like this, and the flash makes every untapped pair of blue mana a live threat.