Primal Reversion

Primal Reversion (Japanese: ゲンシカイキ Primal Regression) is an ancient transformation affecting that debuted in. Pokémon that have undergone Primal Reversion are distinguished by the word "Primal" in front of their species name. Primal Reversion is said to restore a Pokémon's true powers as the Pokémon absorbs the energy of nature to greatly increase its power.

In battle
In order to undergo Primal Reversion, a Pokémon only needs to be holding the appropriate orb. Like Mega Stones, orbs cannot be removed during battle if held by the appropriate Pokémon. Unlike Mega Evolution, however, the player does not need a Key Stone or have to manually trigger Primal Reversion; it will simply happen automatically after the Pokémon enters battle and after any entry hazards take effect, but before the activation of weather-changing.

In a Rotation Battle, the Pokémon will only undergo Primal Reversion if it is sent out in the primary position; the Primal Reversion will not activate if the Pokémon is sent out in a secondary position at the start of the battle and then rotated to the primary position. Also, unlike Mega Evolution and Ultra Burst, there is no limit to the number of times a Primal Reversion may be performed per battle.

In the main series
Primal Groudon and Primal Kyogre both appeared in Mega Evolution Special III, where they had a clash with one another off the coast of Rustboro City. Alain and attempted to fight the ancient Pokémon with their Mega  X and Mega, but they were soon overpowered. Soon after, appeared, battled, and eventually managed to defeat the two Primal Pokémon, causing them to return to their regular forms.

Primal Groudon and Primal Kyogre also appeared in Hoopa and the Clash of Ages, where they were summoned and controlled by along with the creation trio and  to attack, , Hoopa Confined,  Rayquaza, and the Eon duo in Dahara City.

In Pokémon Generations
Primal Groudon appeared in 's vision in The Vision. She imagined it attacking Maxie, Tabitha, and the rest of Team Magma, but this did not deter her from her Team's plans for long.

Primal Kyogre appeared in The Cavern. Despite Shelly's insistence not to, Archie awakened it in the Seafloor Cavern. It proceeded to cause destruction across Hoenn, and eventually prepared to attack Archie and Shelly.

In the Pokémon Omega Ruby and Alpha Sapphire Animated Trailer
Primal Groudon and Primal Kyogre both appeared in the Pokémon Omega Ruby and Pokémon Alpha Sapphire Animated Trailer.

In the Pokémon Adventures manga
In the, Archie and Maxie used the Red and Blue Orbs to transform into their Primal forms in order to help save the  from the giant meteoroid headed for the planet. After some training at the Meteor Falls, both Primal Pokémon managed to master their special moves; and, respectively. However, both ancient Pokémon, even when assisted by, completely exhausted themselves while destroying a large piece of the meteoroid falling before the main body, causing them to revert to their regular forms.

In the TCG
Primal Reversion were brought into the Trading Card Game with the release of TCG Primal Clash (TCG Gaia Volcano • TCG Tidal Storm in Japan). Primal Reversion is an extension of the TCG Pokémon-EX (Mega Pokémon-EX) mechanic, evolving from the long-standing Pokémon-EX. The only Primal Pokémon-EX are the and  cards from Primal Clash and TCG Ancient Origins. Although not exclusive to the mechanic, each Primal Reversion Pokémon features a new card effect named Ancient Trait, providing an additional effect for each card. The Ancient Origins prints feature the shiny versions of the Pokémon, and replaces the original Ancient Traits with θ Max, but are otherwise identical to the Primal Clash cards.