Primal Reversion, much like Mega Evolution, is a temporary evolution that was first introduced within the 3DS remakes Pokémon Omega Ruby and Pokémon Alpha Sapphire. When a Pokémon undergoes Primal Reversion it's said to regain its "original power", aka. it gains various stat boosts and other alterations just like Mega Pokémon do. Many mysteries still surround this new evolution method. It's been teased that Primal Reversion has some sort of connection to Mega Evolution but the exact links have yet to be revealed. For the moment Primal Reversion appears to be a plot-specific evolution method unique to Groudon and Kyorge. Through this reversion these two iconic legendaries are able to transform into their new forms: Primal Groudon and Primal Kyogre. A legend told in the Hoenn region explains how Groudon and Kyogre originally achieved their Primal forms: Be sure to check back as more information is revealed!