Graveler is one of the many Pokémon you can encounter and catch in Pokémon Brilliant Diamond and Brilliant Pearl. It has a second evolution, Golem, which you can get. But you will need to make sure you follow a certain method to evolve it into this final form. Here's what you need to know about the evolution of Graveler into Golem in Pokémon Brilliant Diamond and Brilliant Pearl.
The only way to evolve Graveler into Golem is by trading with another player. You will need to find someone you trust to conduct the trade with and have them return the Golem once the trade is complete. Alternatively, they can trade you a Graveler and when you receive the Pokémon, you will have a Golem instead.
Regardless of how you want to do it, it all comes down to trading with another player. Once the trade is made, Graveler will become Golem when he joins the other player. He doesn't need to contain specific items or know specific moves. You may have done this in previous Pokémon games, such as Red and Blue, Gold and Silver, or even Ruby and Sapphire. Graveler Becoming Golem has been featured in the game series from the very beginning.
We recommend that you do not trade with a casual player online as it is quite easy for them not to return the Pokémon to you after the trade.