You have to trade from R/S/E.
You have to have regiice, registeel and regirock to be able to fight him
you can't. trade with someone who has a ruby, sapphire, or emerald version
The only Regi you can get in Pearl in Regigigas But to get Regirock Regiice and Registeal get them in Sapphire Ruby and Emerald Firered or Leafgreen srry to say that folks
The only way is through migrating them from Pokémon Ruby, Sapphire or Emerald or by trading.
you can find regiice near the dewford town,surf northwest.
in a Nintendo event
route 105 in the ruins.
Have Regirock, Regiice, and Registeel in your party and go to the temple at Snowpoint City and complete the maze thingy. But the only way to get all 3 Regis is to transfer them to Pal Park from a gameboy Pokemon.
you must trade him from either Pokemon ruby, sapphire, or emerald.
you have to migrate from Pokemon emarld
You can get Kyogre,Regirock,Registeel,and Regiice.
Regirock, Regiice and Registeel. if you capture all three and transfer then to Pokemon Diamond/Pearl/Platinum you can go to the shrine in Snowpoint City to battle the master Regigiggas :)