Well after you unlock the doors to the chamber, you either fire ultra balls at it or if u can find a luxury ball use that. it is easier with a luxury ball. I was really lucky. I caught it with my one and only thrown ultra ball. dont get your hopes up that you will because it is insanely hard. bring a bunch of ultra balls. i brought 91 and left the cave, with regice, and 90 ultra balls.
Go in the island cave then use Fly in the middle.
You can only catch it in Ruby, Sapphire or Emerald and migrate it over. If you get an event Regigigas on Pokemon Platinum you can catch Regice there.
you can not get regigigas! but you can catch regice, regirock, registel.
Regirock, and finally Registeel.
go to the sealed chamber and get relichant in front and wailord in last......
you cant you have to get it on emerald/sapphire/ruby then migrate it to pal park
To get regice, you need to either get it from ruby/sappire/emerald, or you can catch it if you have gotten the level 100 regigigas from the event before the release of platinum.
The legendaries you can catch in Pokemon Ruby without trading or going to an event are Groundon, Rayquaza, Latios, Regice, Regirock, and Registeel.
You catch regice
sorry, you can't catch them, you have to migrate them from the GBA game Sapphire/Rubymigrate
there is not regice in pearl. but if you have ruby, emerald, or sapphire you could trade regice,regirock, and registeel to get rigigious.
You can only get a regice, regirock, and a registeel by migrating them from ruby or Sapphire. If you migrtate these Pokemon you can also catch regigigas.
U will need flash for this. once you have flash you stand in the middle of his cave and use flash then go in and catch the FUTHAMUKA