You can catch Rayquaza in your house upstairs after you catch all the legendarys in the game.
You can catch the main white legendary, Kyrugem, Virizion, Cobalion, Terrakion, Thunderous, Victini, Zorua, Zoroark, Volcarona, and Landorus.
Zapdos, Articuno, Moltres, Mewtwo, Entei/Raikou/Suicune (depends on what starter you chose).
You use block or mean look at a lengedary Pokemon and then make it asleep and weaken it. After that, it's pretty easy to catch it. If you wanna catch LUGIA then you weaken it, lure it to sleep, and then it's easy to catch. Pokeballs and ultraballs are good against legendarys.
you cant the only legendarys are regirock, regice, registeel, latias or in your case latios and groudon and the harder to catch rayquaza and deoxys
You can't catch any legendarys in Iron Island.
catch legendarys
You can catch Rayquaza in your house upstairs after you catch all the legendarys in the game.
you keep playing...
You cannot catch both legendaries with a single game.
You complete your pokedex and catch the legendarys
Master Balls, obviouslt
you can find them in rooms like Jimmy's room
Battle the E4 and they will all come back?
you can catch kyogre,latias,rayquaza,deoxys(some say),
You have to catch a Dito with the same nature as the legendary and pute them in the daycare. You catch Dito in trophy garden.
go to serebii.net and look on the left for hggs pokedex and go to the Pokemon you want to catch and it will tell you everything about it