Pokémon Brilliant Diamond and Shining Pearl feature a vast roster of Pokémon to find and catch. These Pokémon are found in a multitude of ways. One of these is the ice and dark-type Pokémon Sneasel.
To catch a Sneasel, you will need to head to the northern part of Sinnoh and look on the snowy routes. This includes Route 216, Route 217, Acuity Lakefront, Lake Acuity, and Snowpoint Temple. Sneasel isn't too hard to find on these routes so it shouldn't take you long.
To evolve Sneasel into Weavile, you are going to first need a Razor Claw. This held item can be found at Victory Road. Once you have it, you simply need to give it to your Sneasal and level them up during the nighttime. This will allow Sneasal to evolve into Weavile.
Sneasel and its evolution Weavile are great Pokémon. They have a unique typing and are some of the only fast ice-type Pokémon. The pair also have a pretty cool design and can learn a good spread of moves that take advantage of their speed and attack.
For more information on Pokémon, check out Best early-game Pokémon in Pokémon Brilliant Diamond and Shining Pearl and How to get the Shiny Charm in Pokémon Brilliant Diamond and Shining Pearl on Pro Game Guides.