This is a guide that covers all the legendaries that can only be located by Soaring in the sky. These legendaries that come from Johto, Sinnoh, and Unova can either by found by their own specific Mirage Islands, or located in the sky. Much like with Ho-Oh, Lugia, and Heatran, you will face them in their own dimension, most of them from a dimensional ring you'll find on foot. The only recommended Poké Balls you can stock on in preparation for this are Ultra Balls and Timer Balls (once enough turns have passed), though Net Balls can still be used for the two Water-type legendaries you will encounter in this quest. Read More...
From Bulbapedia, the community-driven Pokémon encyclopedia.
Overview For those of you who have in their possession an event Regigigas in your party it is possible to be able to collect Regirock, Regice, and Registeel in your game without having to import them from Ruby, Sapphire, and Emerald through Pal Park. They are notably the only non-event legendaries that cannot be found under normal conditions in the Generation IV games (similar to Ho-Oh and Lugia in the Generation III hand-held games). Read More...