Today The Pokemon Company unleashed the nightmarish powers of the "Mythical Dark-Type Pokemon, Darkrai" across a variety of media including via a special character distribution available from Nintendo WiFi Connection service for players of the Pokemon B&W video games, and for players of the Pokemon Trading Card Game, in the form of an extremely powerful "Darkrai-EX" card and a rare "Ultra Full-art Darkrai-EX" card.
These cards can be found in the latest Pokemon TCG expansion, Pokemon TCG: Black & White-Dark Explorers, which arrived at retail today (see "'Pokemon: Black & White-Dark Explorers'").  The Black and White-Dark Explorers Booster Packs may contain a "Darkrai-EX" or any of five other Pokemon--Tornadus, Kyogre, Entei, Raikou, and Groudon as powrful Pokemon-EX.