You will need to find items in Pokémon Brilliant Diamond and Brilliant Pearl which are known as Evolution items. These items allow certain Pokémon to reach their final evolution during use, but finding them can be a bit tricky. King's Rock is one of these elements. In this guide, we will share with you where you can find King's Rock in Pokémon Brilliant Diamond and Brilliant Pearl.
There is only one way to find King's Rock, and that is to catch a Poliwhirl. It should contain this item if you take it from the wild, but only has the option to hold it when you find this Pokémon.
You can find Poliwhirl by searching for it on Route 226 using a Good Rod, or you can find it by exploring the Grand Underground. Poliwhirl will appear in this area once you have completed the game, finished the Sinnoh PokéDex, and unlocked the National PokéDex. Poliwhirl can appear in the Fountain Source Cave, River Bank Cave, and Calm Water Cave. If you are having a hard time finding a Poliwhirl in the Great Dungeon, the best way to increase your chances of finding it is to place Water-type Pokémon Statues in your Secret Base.