The Master Ball is a Poké ball that has assured catch rate of a x255 multiplier. It will always catch a pokémon, great for legendary hunting/low capture rates(It will not capture other Trainer's Pokémon). Master balls are not craftable and are only obtainable from boss Pokémon, Creative mode, Master Ball loot chests or spawning the item in. It is often used to catch legendary Pokémon, or rare Pokémon such as shiny Pokémon.The ID for the Master Ball is 4142, the update for 3.4 makes the ID 4137.
The Master Ball is a rare Pokeball that cannot be crafted. People commonly use it to catch legendaries, high level pokemon or a shiny (Sometimes cheated off creative menu). The Master Ball is usually hard to obtain in servers, because someone has already claimed the loot, servers make them a rare voting reward. Few servers give free master balls as a starting kit or others.