You get it in team aqua's hideout near lilycove. You need a Pokemon that knows surf to get to the hideout. Another way to get masterball are hack and cheats
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.
master ball
a master ball!!!
You can't do that unless you have emerald. then you can clone the master ball.
no there is not
In emerald it is at the space station
cheats
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In team aqua's base
Try harder
you can get a master ball in the team aqua hideout. Its in a room with four poke-balls.
you don't get the master ball from may in emerald, you get it in the team aqua/magma hideout in lilycove. that is the only way to get a master ball , unless you win the loto ticket drawing or use an actionreplay or gameshark.