Mega Rayquaza is a powerful Pokémon introduced in the Pokémon series. It is the Mega Evolution of Rayquaza, a Legendary Pokémon known for its dragon and flying abilities. Mega Rayquaza has a unique ability called Delta Stream, which changes the weather to protect it from super-effective moves. In its Mega form, Rayquaza gains enhanced stats, making it one of the strongest Pokémon in battles. It does not require a Mega Stone to Mega Evolve, which is unusual for Mega Evolutions. This allows it to hold an item while still benefiting from its increased power and abilities.