Tidal Courier is a uncommon Creature — Merfolk card from Duel Decks: Merfolk vs. Goblins (DDT), collector number 19. Current market price: $0.26, TCGplayer market prices via Scryfall.
When this creature enters, reveal the top four cards of your library. Put all Merfolk cards revealed this way into your hand and the rest on the bottom of your library in any order. {3}{U}: This creature gains flying until end of turn.