Pikachu has become the flagship Pokémon in almost every Pokémon game. It is a remarkable and easy to recognize creature. If you catch it, you can evolve it into a Raichu, another Electric-type Pokémon. Here's what you need to know about Pikachu's evolution into Raichu in Pokémon Brilliant Diamond and Brilliant Pearl.
There is only one way to evolve your Pikachu into a Raichu. You will need to do this by giving him a Thunder Stone. You have two locations at your disposal to find it. One of them is in Sunyshore City. You can only reach this position after you've defeated Team Galaxy and are ready to take on the eighth Gym Leader.
If you'd rather not wait that long, you can always look for it in the Grand Underground. Unfortunately, you'll need to complete the Fossil Digging minigame to potentially find one underground, and there's no good way to tell if you have one waiting for you or not. These are considered rare items. You can increase your chances of finding one by running through the Diglett or Dugtrio you encounter on your travels through the Grand Underground. The higher this bonus is while you're down there, the better your chances of finding rare items.