Catching Pokemon has always played a central role in Pokemon games, with most of the series' mainline entries having hundreds for players to track down and capture. Pokemon Brilliant Diamond & Shining Pearl has 493 of them, with certain Pokemon being a lot harder to catch than others. In particular, some of the Legendary Pokemon found in the games have ridiculously low catch rates, meaning that even when using Ultra Balls, there's still a certain level of RNG involved. Players can technically remove all doubt, however, but only if they happen to have a Master Ball.
Ever since the Gen 1 games, Master Balls have provided players with a sure-fire way of catching Pokemon. Unlike regular Pokeballs, which often require players to weaken Pokemon in order to be effective, a Master Ball has a 100% catch rate regardless of a Pokemon's health or status. There is something of a catch, however, as Master Balls are traditionally incredibly rare, and this is once again the case in Brilliant Diamond & Shining Pearl.
Where to Find Master Balls in Brilliant Diamond & Shining Pearl
There is only one sure-fire way to get a master ball in Brilliant Diamond & Shining Pearl, and it only presents itself once players have beaten the game's seventh gym leader, Candice. After doing so, players will need to stop in at Lake Acuity to take care of Team Galactic and then return to Veilstone City. There, they should head to Team Galactic's headquarters in the northeastern corner of the town, where a former Grunt will leave behind a Storage Key after he flees.
With the Storage Key now in hand, players should head over to the place where they found the Fly HM earlier on in the game, as it's there that they'll be able to use the key to gain access to the basement area of Team Galactic's HQ. They'll need to follow the around path to the right and then enter the main building, where they'll need to use the many yellow teleporters to explore. Eventually, players will find themselves back in the basement, where, after making their way to the left, they'll be able to find a Galactic Key.
After picking up the key card, players should exit through the door to their left and make their way outside, and back over to the HQ's main entrance. They'll now be able to open the locked door in the lobby area, which will lead them to some more teleporters and, eventually, the building's upper floors. Here, they'll run into the leader of Team Galactic once more and will need to defeat him in battle before they can progress. Once they've done so, Cyrus will hand over a Master Ball as a reward.
The Best Pokemon to Use Master Balls on in Brilliant Diamond & Shining Pearl
Given that Legendaries typically have the lowest catch rates, players will almost certainly want to save their Master Ball for one of the games' heavy hitters. Palkia & Dialga are particularly hard to catch, so many players opt to use their Master Ball picking up their game's mascot Pokemon a little further on in the story. Other viable candidates include Mewtwo, Rayquaza, and Giratina, though players will have to wait until after they've completed the main story before even getting a chance to catch one of those.
Other Ways to Get Master Balls in Brilliant Diamond & Shining Pearl
There is one other way to get a Master Ball in Brilliant Diamond & Shining Pearl, though it is far from guaranteed. It requires players to visit the TV Station in Jubilife City, where they'll be able to enter a special lottery to win a second Master Ball. It's very unlikely that players will win it, however, so they really shouldn't hold their breath. That said, it stands to reason that at least some players will win one, so it definitely can't hurt to try.