Obscuring Aether is a rare Enchantment card from Dragons of Tarkir (DTK), collector number 194. Current market price: $0.19 (foil $1.16), TCGplayer market prices via Scryfall.
Face-down creature spells you cast cost {1} less to cast. {1}{G}: Turn this enchantment face down. (It becomes a 2/2 creature.)