You get it when you raid the Team Aqua hideout in the Cave in the Cove (Lilycove City). If you need help, check below....
OK so a couple of Aqua goons are standing on the beach, talking about what Team Magma are doing. You have to defeat Team Magma (found near Lavaridge Town) before they move. Then, when you get inside, some more are blocking the entrance. They - being idiots - tell you that the Boss has gone to Slateport for something-or-other (I can't remember what, sorry). Solve the problem there, then head back to Lilycove. The goons are gone. Now, you have to find your way through the Aqua hideout. The white things are warp panels, which take you to a different place. You do the math.
NOTE: You need to explore the innermost chambers of the Aqua hideout to find the Ball.
you have to clone that Pokemon holding a master ball
a master ball!!!
You can copy a master ball on Pokemon Emerald by having one of your friends that has one sign on to their ds and connect the two. Then they can give it to you in the Pokemon center.
You can't get another master ball in emerald because there's no one will give you the master ball just the general will give you that.
capture legendary Pokemon like rayquaza.
No.
You can't do that unless you have emerald. then you can clone the master ball.
first you get amaster ball give the master ball to Pokemon copy that Pokemon over and over again then take the master balls from the Pokemon
you can get a master ball in the team aqua hideout. Its in a room with four poke-balls.
you can use master ball in caught the groudon
Clone your Pokemon and give them the master ball
For Pokemon emerald via gameshark Master code: D8BAE4D9 4864DCE5 Master ball code: 82005274 0001 The master ocde is very important. You will get master ball in any pokemart for free after you type the "Master code" and the "Master ball code". HOPE IT WORKS!