Elvish Harbinger is a uncommon Creature — Elf Druid card from Duel Decks: Elves vs. Goblins (DD1), collector number 4. Current market price: $7.55, TCGplayer market prices via Scryfall.
When this creature enters, you may search your library for an Elf card, reveal it, then shuffle and put that card on top. {T}: Add one mana of any color.