The best Poké Ball you can use in any Pokémon game is the Master Ball. With it, you are sure to catch any wild Pokémon you come across. Unfortunately, it is also a rare Poké Ball. You will not be able to find it in a mall or shop in the game. In this guide, we will share with you where you can find the Master Ball in Pokémon Brilliant Diamond and Brilliant Pearl.
You will receive a Master Ball as you progress through the story. First, you'll need to make your way to the seventh Gym Leader, meet Team Galaxy in Lake Acuity, and then run after them at their headquarters in Veilstone City. When you reach the interior of their headquarters, you will face their leader.
After beating the leader of Team Galactic, he will have a brief discussion with you about their plans. For defeating him, he will also reward you with the Master Ball. You will receive it before reaching the eighth Gym Leader so that you can receive it before the end of your Pokémon Brilliant Diamond and Brilliant Pearl journey. You will need to make sure you are using the Master Ball on a useful Pokémon. You will always also catch the Pokémon you use it on.