Obtain the PokeGods: To evolve Blastoise, Charizard, and Vensaur into Rainer, Charcoalt, and Sapusaur, you need to get behind Bill's house. Once there, you'll be an an area called Kalos (mistranslation of "Colors"), and you can obtain the stones needed (Mist Stone?) to evolve them into their most powerful forms. If you beat the Elite Four enough times you can even get stones that let you evolve Beedrill into Beepin, Gengar into Spooky, and even Mewtwo!!!