keep it if your playing Pokemon Sapphire for the rare kyogre.
You should save it for later to catch Latios.
Catch Groudon.
you get a master ball from someone. use it. he's AWESOME!save your master ball for latios use an ultra ball to catch groudon that's what i did and it worked
It is best to get rayquaza. Use mean look on latias and latios, it'll stop them fleaing.
It really depends. If you aren't going to use your master ball on anything else, then using it on Groudon is fine if you want to. But you can catch it with a Poke ball or Great Ball, etc. Use dusk balls or ultra balls. It is not worth it to use masterball because groudon is not so hard. I caught groudon with only 3 ultra balls.
you can if you have a Master Ball
You should use a master ball.
you can use master ball in caught the groudon
you can with ultra balls or if your stupid waste your master ball-PS i caught groudon with a heavy ball (he weighs more than two thousand pounds) so that might be to him a master ball
After defeating Cyrus in Veilstone, he should give a Master Ball to you.
NO WAY! sorry for those of you that it is too late for, but you should save your master ball for Mew or Mewtwo!
A master ball