You get it from the Galictic boss Cyrus in the Veilstone Hq. But you need like 7 badges first!
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Located in the Galactic Veilstone Building after defeating Cyrus.
Also given away as a prize at Jubilife TV, for matching all 5 numbers in the lottery.
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
there is no more masterballs in Pokemon platinum but not if you use cheats
Master Ball.
with a master ball
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.
not possible