When Pokémon Omega Ruby and Pokémon Alpha Sapphire is released on November 21st in North America and November 28th in Europe, it will contain a special new story segment called Episode Delta. in this story segment the player will need to begin a quest to save the world. The Pokémon Company and Nintendo have released a story summary of what the quest will contain below:
Pokémon Omega Ruby and Pokémon Alpha Sapphire introduce a new story, the Delta Episode, which reveals the history of the Hoenn region and thrusts Trainers into a quest to save the world. The Mossdeep Space Center, a research facility for studying space and rocket science, discovers that a giant asteroid is hurtling toward the planet. Trainers must stop Team Magma and Team Aqua from attacking the facility. Meanwhile, a battle in space is brewing between the Sky High Pokémon Rayquaza and the DNA Pokémon Deoxys, a powerful Pokémon that can transform between four distinct Formes: Normal Forme, Attack Forme, Defense Forme, and Speed Forme. Rayquaza faces a fateful challenge that will determine the future of Hoenn.
Helping trainers restore peace to the Hoenn region are Sootopolis City’s Gym Leader, Wallace, and the Hoenn region’s Champion, Steven, both of whom hold secrets to stopping the asteroid. Trainers will also meet Zinnia, a mysterious girl rumored to possess the key to the fate of the world. Zinnia wears a Mega Anklet set with one of the mysterious Key Stones, which allows her Salamence to Mega Evolve.
You can check out a trailer focusing on Episode Delta below where it also talks about the various Mirage Spots throughout Hoenn and the legendary Pokémon that can be found there.