You get one and only one after you defeat the team galactic boss or if you trade.
The only way to get another master ball in Pokemon dimond whithout cheating is by giving a Pokemon a master ball as an item in another game and trading that Pokemon to your Pokemon dimond game and take the master ball then you can use it. Or you can get an action replay at www.amizon.com for $20.00 and find the master ball cheat for it then you can get lots of master balls all the time it realy works try it.
you can't get 999 master ballsdon't waste it on dimond or pearl they can be caght with a ultra ball OK.
Buy an action replay works for Pokemon pearl dimond and platinum
belive it or not light balls only appear in Pokemon dimond and pearl
Getting master balls without cheating in Pokemon DP is very hard. The only ways are: to win the lottery in Jubilife City, or receive a Pokemon that has a master ball from trading. I have 2 master balls in my game. I traded with a person who had a Pokemon with a master ball.
Buy them stupid
You trade Pokemon from friends that's Pokemon is holding a master ball
Clone your Pokemon and give them the master ball
give one to a Pokemon and trade the Pokemon with the master ball.
you can't.
you can't
That depends on the Pokemon game.