Pokémon: Mega Evolution Special III (Japanese: ポケットモンスターXY特別編 最強メガシンカ ～Act III～Pocket Monsters XY Special Episode: The Strongest Mega Evolution ~Act III~) is the third Mega Evolution Special and the third special episode of the XY series. It first aired in Japan on March 19, 2015 and in the United States on August 15, 2015.
In this third installment of the four-part series, Alain, Mairin, and Steven arrive at the Devon Corporation in Rustboro City, where they make contact with Alain’s boss, Lysandre. Lysandre informs the trio that Primal Groudon and Primal Kyogre have appeared and are both moving towards a mysterious energy source that is suspected to be the missing Giant Rock.
Steven recounts the legend of the ancient times when Groudon and Kyogre struggled against each other to expand the continents and the seas. The two battled over a source of enormous energy with such ferocity that it nearly destroyed the world. Unfortunately, this legend seems to be playing out again!
Steven analyzes the Legendary Pokémon’s separate paths towards the Giant Rock and determines that they will cross paths in the ocean off the coast of Rustboro City. Despite Mairin’s objections, Alain and Steven travel to the meeting point to observe as the two Pokémon collide near the Giant Rock and engage in an epic battle. Lysandre gives Alain orders to protect the Giant Rock at all costs.
Alain and Steven send Mega Charizard X and Mega Metagross out to battle Primal Groudon and Primal Kyogre, but they prove to be a mere distraction. The situation seems bleak—particularly when Mega Rayquaza arrives to join this all-out battle! Just as it appears that Mega Rayquaza will claim the Giant Rock, a submarine emerges from beneath the waves and pulls the Giant Rock into its hull via a powerful energy shield.
Lysandre contacts Steven from the submarine, confirming that he’s taking the Giant Rock to Kalos. As the situation settles, Alain leaves Mairin to return to Lysandre Labs to continue his training, but Steven and Mairin decide to follow their friend.
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