>>46873787The Regis are the pure elemental forces, either created by Regigigas or by Regigigas' creators. They balance out the Earth created by the Weather Trio; Regigigas pulled the Continents together before shutting down and presumably the other Regis played a role in imbuing the newly formed Earth with its elemental properties.
Something shut the Regis down and trapped their pure elemental power in the Plates. There's no reason to think Regigigas fought other Regis, something else did it - possibly early Humans who wanted to use their elemental power to manifest Arceus.
