I caught Regirok and Regice,but I got Registeel by trade. Will I be able to get Regigigas?
In short, yes.
To get Regigigas, you go into the room behind the one with the frozen rock (in twist mountain) and Regigigas will be in there. Also you need to have Regirock, Regice, and Registeel in your party when you go there.
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