Question

From where you get national dex?

Answer 1

See all the sinnoh pokemon, including legendaries then talk to proffessor Rowan and he will give you it.

Comments

Omg I need to see all 493 pokemons offff omg

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Not 493, just the 210 Pokemon in Sinnoh.

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I suggest you finish the game before trying to finish the pokedex . You'll see more by that way. If you already did that , there are many ways for you to get the remaining Pokemon . And by this time , there should only be a few left.