Nashi, Moon Sage's Scion is a mythic Legendary Creature — Rat Ninja card from Secret Lair Countdown (SLC), collector number 2022. Current market price: $6.01 (foil $8.66), TCGplayer market prices via Scryfall.
Ninjutsu {3}{B} ({3}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.) Whenever Nashi deals combat damage to a player, exile the top card of each player's library. Until end of turn, you may play one of those cards. If you cast a spell this way, pay life equal to its mana value rather than paying its mana cost.