Deploy the Gatewatch is a mythic Sorcery card from Eldritch Moon (EMN), collector number 20. Current market price: $0.47 (foil $2.60), TCGplayer market prices via Scryfall.
Look at the top seven cards of your library. Put up to two planeswalker cards from among them onto the battlefield. Put the rest on the bottom of your library in a random order.