Mesmeric Fiend is a common Creature — Nightmare Horror card from Duel Decks: Sorin vs. Tibalt (DDK), collector number 7. Current market price: $1.03, TCGplayer market prices via Scryfall.
When this creature enters, target opponent reveals their hand and you choose a nonland card from it. Exile that card. When this creature leaves the battlefield, return the exiled card to its owner's hand.