Rayquazah! is a Dragon / Flying-type Pokemon that lives in the Ozone Layer. If you go to Anthian City - Battle District, you will see a guy and if yoou talk to him, he will mention you somethng about a "Sky Snake". This could mean Rayquaza will be added in the game shortly. It is still not in the game currently but some players used to be able to buy it from lando64000 for 15 R$. However, this is no longer possible, most likely because no one likes pay 2 win players.