Cyrus gives it to you after you beat him at the warehouse in Veilstone city.
After defeating Cyrus in Veilstone, he should give a Master Ball to you.
a master ball
with a master ball or timer 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.
with a master ball
Master Ball.
i used my master ball
you can not get a master ball in Pokemon platinum only the one professor Rowan gives you
master ball
Master ball
Ultra Ball
go to jubilife and a lottery will be in a building. if first place they will give you a master ball