you need the code here it is Wild Pokemon Modifier
94000130 FDFF0000
B21C4D28 00000000
B0000004 00000000
94000130 FEFF0000
00000890 01ED0001
D0000000 00000000
DA000000 00000892
DC000000 00024620
C0000000 0000000B
D7000000 00000000
DC000000 00000006
D2000000 00000000
1. Press L+R at the inventory screen, then you'll get 493 Masterballs.
2. Set Masterballs' quantity to the Pokemon's number you want. (Example: Mew=Pokemon number 151, discard until you have 151 Master balls)
3. Hold L and encounter Pokemon. DO NOT push L+R together again or you will have 493 Masterballs again (unless you want Arceus as his Pokemon number is 493)
good luck
Action replay
Action replay is not an Pokémon item that can be obtained in Diamond.
Go to neoseekers.com
No
no you have to get is from an action replay or go to a Pokemon event
action replay
action replay
action replay
action replay
its a cheat
Action replay.
Find an action replay code and program it, that's how you get many masterballs on Pokemon diamond action REPLAY. ;)