To help promote the release of the upcoming game
Pokémon + Nobunaga's Ambition (ポケモン+ノブナガの野望) which will be released in Japan on March 17th, 2012, Nobunaga's Dark Rayquaza (ノブナガの黒いレックウザ) will be distributed on the Nintendo Wi-Fi Connection to players of the Japanese versions of
Pokémon Black and White (ポケットモンスター ブラック・ホワイト). The Rayquaza will be distributed from
March 17th, 2012 until April 16th, 2012. This Rayquaza will also be distributed at all the Japanese Pokémon Centers and at Pokémon BW Searcher (ポケモンサーチャーBW) tour locations.
The details of Nobunaga's Dark Rayquaza are as follows:
Sources:
http://www.pokemon.co.jp/info/2012/03/120302_g01.html,
http://www.pokemon.co.jp/info/2012/02/120224_e01.html and
http://game.watch.impress.co.jp/docs/news/20120302_516159.html