The Pokémon TCG M Gengar EX XY166 Promo is a highly sought-after collectible card from the XY set. This special card features the powerful Gengar Pokémon in a slightly modified form, making it a unique addition to any Pokémon TCG collection. With its promo designation, this card likely holds special significance for collectors and fans of the game, making it a valuable and treasured item for enthusiasts of Pokémon TCG.