Having made your way through Victory Road in Pokémon Brilliant Diamond and Shining Pearl, you'll come to the Pokémon League.
Four tough opponents stand between you and the ultimate battle, the third of which is Flint.
How to beat Elite Four Flint in Pokémon Brilliant Diamond and Shining Pearl
When it comes to facing the Elite Four, you're going to have to use your full team. It's a big step up from the Gyms, which you can easily stomp, and Elite Four Pokémon are all going to be above level 50.
As such, it's worth taking the time to train your Pokémon, teach them moves via TM, and generally try to have a spread of types in your party.
While he focuses on Fire-type Pokémon, his team only actually contains two of that type.
Rapidash and Infernape should be easy enough to beat with Water-type Pokémon, for example, but Steelix hits hard and is incredibly tanky, Drifblim is the super-annoying Ghost-type, and Lopunny can run through any team weak to Fighting-type moves.
Make sure you heal up and save your game following the fight, and prepare to face Lucian.