Dont waste your master balls
When you are going after legendaries, don't use your masterball. Save it for latios. You can weaken the regi's down enough to use an ultra ball or even a great ball. For groudon, make sure that you either save before you battle him or use a Pokemon that isnt super effective against him. If you kill him, you can turn off the GBA and start over where you saved. Weaken him down and bring about 40 ultra balls. It will take a while, but you can catch groudon without wasting your master ball.
P.S. To unlock the regi's it is hard to find the fish you need. Here's what I did: Get a tropius and use sweet scent underwater near sootopolis, it will take a while, but eventually he will come
More tricks, tips and cheats for this game are right here - Pokemon Ruby cheats
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