Silent-Blade Oni is a rare Creature — Demon Ninja card from New Capenna Commander (NCC), collector number 352. Current market price: $4.46, TCGplayer market prices via Scryfall.
Ninjutsu {4}{U}{B} ({4}{U}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.) Whenever this creature deals combat damage to a player, look at that player's hand. You may cast a spell from among those cards without paying its mana cost.