Mental Vapors is a uncommon Sorcery card from Gatecrash (GTC), collector number 72. Current market price: $0.09 (foil $0.54), TCGplayer market prices via Scryfall.
Target player discards a card. Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)