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Rayquaza (Japanese: レックウザ Rayquaza) appeared in the movie Destiny Deoxys. It is voiced by Katsuyuki Konishi in both English and Japanese.
This Pokémon, like most other featured legendary Pokémon, proved to be extremely powerful, and it was possibly one of the most powerful Pokémon ever featured in the history of the anime. It fights against Deoxys because it is seen as invading its territory. After a destructive battle over a glacier witnessed by Professor Lund, Yuko and Lund's son Tory, and although it takes a few Psycho Boosts and is critically hit and falls into the freezing ocean, Rayquaza comes back and defeats Deoxys with a Hyper Beam attack.
Four years later, Deoxys manages to regenerate, and it goes to find its friend, a fellow Deoxys, Rayquaza senses its presence and goes to LaRousse City to battle Deoxys again. After LaRousse City has been evacuated because of the Dragon-type's arrival there, Rayquaza manages to break through Deoxys's city-wide barrier after many failed attempts. Then, Rayquaza and Deoxys have a second spectacular battle that destroys some of the city. After Deoxys finds its friend and helps fight off the malfunctioning security bots after Rayquaza becomes engulfed in the security cubes, and the 2 Deoxys come to protect it, Rayquaza realizes that the Deoxys are good and stops attacking.
It also has a cameo in the opening to the ninth Pokémon movie and is captured by Team Rocket.
Its current status is unknown, possibly flying around in the atmosphere (assuming, of course, that it wasn't captured by Team Rocket or it was and had somehow managed to escape from it's prison).
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For more information on this Pokémon's species, see Rayquaza.