Defeat Cyrus at the Veilstone Galactic Building.
go to jubilife and a lottery will be in a building. if first place they will give you a master ball
master ball
no
you can not get a master ball in Pokemon platinum only the one professor Rowan gives you
with a master ball or timer ball
Master Ball.
with a master ball
there is no more masterballs in Pokemon platinum but not if you use cheats
After defeating Cyrus in Veilstone, he should give a Master Ball to you.
Master ball
Ultra Ball
In Pokémon Platinum, Cyrus, the leader of Team Galactic will give you a Master Ball once he surrenders his plans in his Veilstone Headquarters.