Biology:
Rayquaza is a large, green, serpentine Pokémon that also resembles a missile. It has red-tipped, rudder-like wings on its shoulders and down its body, and similarly patterned fins on the tip of its tail. Yellow ring-like symbols run across the length of Rayquaza's body and it has an additional yellow ring on top of its head. Rayquaza has two limbs with three-clawed hands, and two long, flat, horn-like structures on its head, with two shorter horns along its jawline. It has small, yellow eyes with black pupils, prominent pink gums, and two discernible fangs in its upper jaw.

Rayquaza has a strong and endless desire to do heroic deeds for the Pokémon world.[1] Rayquaza can halt the endless battles of the other two super-ancient Pokémon, even in their Primal Forms.[2][3] Rayquaza is the only one who can stop the duo and restore order to nature. Rayquaza is said to have lived for hundreds of millions of years in the ozone layer, where it feeds on water and other particles. It also preys on the Minior above the Alola region and even feeds on meteoroids, particularly Mega Stones. Rayquaza is rarely seen by people; even in flight, its appearance is indistinguishable from that of a meteor. It can breathe in outer space. Rayquaza can be summoned atop Sky Pillar by a Key Stone.

Rayquaza possesses some of the strongest attack power out of any Pokémon; it can easily summon cyclones to overwhelm its opponents. It can soar into the sky and droop out into its foes at high speeds, causing huge damage. Thanks to its weather-manipulation powers, it can eliminate weather effects. Rayquaza was worshiped by the Draconid people along with the people of Hoenn as the savior of the region. Thus, they built the Sky Pillar to honor it. In the manga, the Draconids referred to it as their "Dragon Lord". It is one of the longest-lived Pokémon species. Rayquaza loves Rayquaza Treats made by Snacksworth, who once encountered it in the past. Inside Rayquaza's body lies an organ that contains the same power as a Mega Stone. A Devon Corporation scientist named this organ the mikado organ (Japanese: ミカド器官). By consuming meteoroids as it flies through the stratosphere, the organ will be filled with enough energy to enable Rayquaza's Mega Evolution.

Rayquaza is bitter enemies with Deoxys, with the two often clashing with each other, as depicted in the movie Destiny Deoxys and the games Omega Ruby, Alpha Sapphire and Masters EX.