Chapter 382 - 381: Poliwag!
Politoed!
This is the alternative evolution of Poliwhirl, though its evolution conditions are quite strict.
In the Pokémon world, no one should yet know how it evolves or from which Pokémon it originates.
But Cain knew.
Politoed evolves when Poliwhirl uses the item King's Rock.
King's Rock!
In the Pokémon world, only two Pokémon evolve using King's Rock: one is Slowpoke, which evolves into Slowking, and the other is Politoed.
According to some of Cain's memories, one of Kanto's Elite Four members, Lorelei, the Ice-type Trainer, had a Politoed with the hidden ability Drizzle.
The reason Cain considered Politoed was precisely because of its hidden ability, Drizzle, making it one of the key Pokémon for a rain-based team and a core for this type of strategy.
Of course, Cain currently owned a King's Rock, but if Slowpoke decided to use it to evolve into Slowking, there wouldn't be another one available.
Even so, it wasn't a big problem, as Poliwhirl's hidden ability is Swift Swim, making it an excellent candidate for a rain team.