There are more Pokémon than you can find in Pokémon Brilliant Diamond and Brilliant Pearl. Many of them have specific evolution requirements if you want them to reach their final form. There is a particular requirement that you will have to fulfill if you want to evolve Mantyke into Mantine. Here's what you need to do to evolve Mantyke into Mantine in Pokémon Brilliant Diamond and Brilliant Pearl.
The only way Mantyke becomes a Mantine is if you have Remoraid in your party. This is a specific Pokémon that you need to find this Pokémon throughout the Sinnoh region, but you will need to catch it using a good rod. If you don't have a good rod, it won't spawn while you're fishing.
Once you have Mantyke and Remoraid in your party, all you need to do is level up your Mantyke and become a Mantine. We recommend that you follow this method to facilitate your Mantine search. Mantyke is a Pokémon you can encounter in the Grand Underground, and Mantine is a little more difficult to spot. Evolving a Mantyke every time you find it is much easier. Thankfully, Remoraid is easy enough to catch using a good rod, so getting to Mantine won't take you too long.
