How do you fight regigigas?

Answer 1

You first have to have Regice, Regirock, and Registeel in your party, who you can only battle if you have the Regigigas that you received from a Nintendo Event included in your party. You can find Regice at the Iceberg Ruins in Mount Coronet, Regirock in the Rock Peak Ruins on Route 228, and Registeel in the Iron Ruins in Iron Island. You can find Regigigas in Snowpoint Temple, and you can get into Snowpoint Temple by by defeating the Champion, Cynthia, for the first time.