Kitsune's Technique is a rare Instant card from Teenage Mutant Ninja Turtles (TMT), collector number 229. Current market price: $0.79 (foil $0.88), TCGplayer market prices via Scryfall.
Sneak {1}{U} (You may cast this spell for {1}{U} if you also return an unblocked attacker you control to hand during the declare blockers step.) Target opponent mills half their library, rounded up.