If you currently having Pokemon Omega Ruby or Alpha Sapphire, you have the ability to claim a free Level. 70 Shiny Rayquaza with the Dragon Ascent Move from the Nintendo Network (Mystery Gift) from August 12, 2015 until September 14, 2015.
To claim Shiny Rayquaza in your game:
1. Select MYSTERY GIFT on the main menu, and then RECEIVE GIFT.
Select YES to confirm.
2. Select GET VIA INTERNET, and then select YES to confirm.
3. Watch as you receive Shiny Rayquaza!
4. Resume the game, make sure you have an empty space in your party, and speak to the delivery girl in any Pokémon Center to add Shiny Rayquaza!
5. Be sure to save your game!