Unfortunately, in Pokemon games, the player rarely gets more than one masterball. And Pokemon Emerald is no exception, but this particular version has several glitches and bugs that you can take advantage of to get more masterballs. Will you be patiently waiting for the lottery masterball, or will you take a different, less honest path?
Steps
Method 1 of 2: Winning a Masterball in the Lottery

Step 1. Catch all the Pokémon
You may have already completed this step, but if not, remember that there are tons of ways to catch all the Pokémon.
To win the extra lottery masterball, you must match the lottery ticket number with your Pokémon ID. Catching more Pokémon increases your chances of winning

Step 2. Go to the city of Lilikov
Here you will find the Lilikov department store - the largest department store in the Hohenn region and the place where you can get your lottery ticket.
A random number is generated every day, so you have a chance to win

Step 3. Get your ticket
When you enter the Lilikov department store, the secretary on the right will offer you a “Pokemon Lotto Ticket”. If you accept the ticket, the secretary will give you the number and then check it against the number of the Pokémon in your collection.
Compare all numbers and win the masterball
Method 2 of 2: Cloning a Masterball

Step 1. Take out the masterball
The only masterball in Pokemon Emerald is in Team Aqua's hideout. To get it, you have to go through a maze of teleports. The masterball itself will be in the upper left corner of the central room on level B1.

Step 2. Head to the Battle Tower
After defeating the Elite Four, a new area will appear south of Route 130 - the Battle Line. Here you will find the Tower of Battles, where you can use the glitch and clone Pokémon and items.

Step 3. Place the Pokemon in an empty box on your computer
Equip the Pokémon with a Masherball, as this glitch clones the Pokémon and all the items it is wearing. Before starting the cloning process, you should save the game.

Step 4. Send the masterball Pokémon to Link Multi Battle
Talk to the first girl at the counter on the right to enter the Link Multi Battle. Choose a Pokémon holding a masterball.

Step 5. Stop saving
When the game starts to save (before you enter the battlefield), you must turn off the console. Turn on the game to complete the cloning process.
You must turn off the game during the "Save, do not turn off the power on the console" warning

Step 6. Return to the box
As a result, the bug will overwrite the selected slot with one of your Pokémon to the one in which the Pokémon with the masterball was saved. Now you will have another Pokemon of the same, as well as a second masterball.
Warnings
- Do not put it in a box with another Pokémon to avoid accidentally overwriting the data of the Pokémon you want to save.
- Bugs can sometimes lead to unwanted side effects. If the bug doesn't work, you could lose your Pokémon, or worse, ruin your save file.