Foul Emissary is a uncommon Creature — Human Horror card from Eldritch Moon (EMN), collector number 158. Current market price: $0.23 (foil $0.10), TCGplayer market prices via Scryfall.
When this creature enters, look at the top four cards of your library. You may reveal a creature card from among them and put it into your hand. Put the rest on the bottom of your library in any order. When you sacrifice this creature while casting a spell with emerge, create a 3/2 colorless Eldrazi Horror creature token.