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The Poké-devil has appeared and offered you a deal: He'll give you any Pokémon you want to have on your quest to be the very best, like no one ever was. The catch: All of these Pokémon must share one type in common, and you have to raise them from level 1. Choose your team of six, go forth, and conquer. Who do you choose?
Easy mode: All types and Pokémon are fully allowed.
Normal mode: The shared type can't be Dragon or Steel, and "god"/uber legendaries like Groudon, Arceus, or Darkrai aren't allowed.
Hard mode: Nothing on your team can have Dragon or Steel as its other type, either, and no legendaries of any kind are allowed (i.e. your mono-Psychic team can't even have Mesprit in it).
Champion mode: Your team must consist entirely of single-type Pokémon of the same type.