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Delta Stream
>When a Pokémon with Delta Stream enters the battle or a Pokémon gains the Ability Delta Stream, the Ability creates strong winds, a unique weather condition. The strong winds last as long as the Pokémon with Delta Stream is in battle with the Ability. In a Rotation Battle, Delta Stream will not activate if the Pokémon is sent out in a rotated-out position and will not activate if the Pokémon is rotated in; the strong winds will dissipate if the Pokémon is rotated out.
>Strong winds cause moves that would be super effective against pure Flying-type Pokémon to instead deal neutral damage to all Flying-type Pokémon. Outside of Inverse Battles, this causes Electric-, Ice-, and Rock-type moves to deal neutral damage to Flying-type Pokémon; during Inverse Battles, this causes Bug-, Fighting-, Grass-, and Ground-type moves to deal neutral damage to Flying-type Pokémon. If a move is not super effective against the Pokémon's other type (for dual-typed Pokémon), this no longer counts as a super effective hit (for the purposes of damage-reducing Berries, etc.). Strong winds have no effect on Stealth Rock or Anticipation.
Additionally, strong winds cause the weather modifying moves Sunny Day, Rain Dance, Hail and Sandstorm to fail if used; and they cause the Abilities Drought, Drizzle, Sand Stream and Snow Warning to fail to activate.
>If Delta Stream is suppressed or replaced, the strong winds it causes will disappear. If another Pokémon in battle has the Ability Desolate Land or Primordial Sea, the dominant weather condition will be determined by whichever Ability activated last.
