Ethereal Ambush is a common Instant card from Fate Reforged (FRF), collector number 152. Current market price: $0.07 (foil $0.13), TCGplayer market prices via Scryfall.
Manifest the top two cards of your library. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)