Darkmoon Fortune Tellers are what they are, fortune tellers affiliated with the Darkmoon Faire. They are summoned from the inscribed Darkmoon Faire decks. When one obtains a deck, a quest will be offered and by accepting and using the deck, a fortune teller will appear and offer you nice rewards. These fortune tellers can be summoned pretty much anywhere, from cities to fierce battlegrounds to dangerous raids and dungeons.
They are dressed in a green robe with the Darkmoon Faire tabard, have a pointy green "witch" hat and a staff with a glowing orb.