On the 11th floor of Silph Co., you'll confront Giovanni for the second time. His team will be stronger than before, featuring Pokémon like Nidoqueen, Nidoking, and Kangaskhan. Have a diverse team ready, with strong Psychic, Water, or Grass-type moves. Defeating Giovanni will force Team Rocket to retreat from Silph Co., and the President will reward you with the Master Ball, the ultimate Poké Ball that catches any Pokémon without fail.
