Mare Primordiale (Primordial Sea)

Primordial Sea transforms the battlefield into an overwhelming aquatic environment that goes far beyond ordinary rain conditions. When Primal Kyogre enters battle, this ability immediately establishes heavy rain that functions like a permanent Rain Dance effect, boosting Water-type moves by 50% and enabling Thunder to bypass accuracy checks. However, the defining characteristic of this primordial weather is its complete nullification of damaging Fire-type moves, causing them to fail entirely rather than simply reducing their power.

The weather control exerted by Primordial Sea is absolute and cannot be overridden by conventional weather-changing moves or abilities like Drought or Sand Stream. Only the other primordial weather abilities, Desolate Land and Delta Stream, can replace heavy rain, creating interesting dynamics in battles between the weather trio. While Air Lock and Cloud Nine can suppress the effects of heavy rain, allowing Fire moves to function normally, they cannot actually change the weather itself, meaning the heavy rain persists but becomes temporarily ineffective.

This ability makes Primal Kyogre an incredibly dominant force in competitive play, as it essentially removes an entire type from offensive consideration while simultaneously empowering Water-type attacks. The permanence of the weather effect ensures that Primal Kyogre's team can rely on consistent rain support throughout the battle, making it a cornerstone of rain-based strategies and a formidable check to Fire-type threats.