professor elm gives it to you..
Duplicate Pokemon with a masterball attached to them.
After you have defeated all 8 gym leaders, go to prof. elm. He will give you the masterball.
After defeating Team Rocket, you need to go to Prof. Elm. He will give you a Masterball if you talk to him.
use a masterball.
blablablablablablablabla
After you beat the game, it will become a roaming pokemon. It will run after the first turn, I suggest using the masterball or using a strong wobbufett. -CrystalManiac
You find it in the team aqua hideout.
from your enemy teams base
Team Magma Hideout
In team aqua's hideout
You can only get one
In Pokemon Crystal.