Dusclops is a Ghost-type Pokemon that trainers can evolve into Dusknoir while playing Brilliant Diamond and Shining Pearl.
Dusclops has seen a rise in competitive play over the last few years, leaving its final form of Dusknoir in the dust. Trainers are still likely to evolve Dusclops to obtain Dusknoir for the sake of their Pokedex.
If you want to evolve your Dusclops, first you will need to obtain one. From there, you will need to trade Dusclops to another player with a Reaper Cloth and have it traded back once it evolves.
Where to catch Dusclops in Pokemon Brilliant Diamond and Shining Pearl
As a prerquisite, you will need to have beaten the Elite Four and become the Champion in Pokemon Brilliant Diamond and Shining Pearl. After that, you must unlock the National Pokedex by having seen all Sinnoh Pokemon.
After these conditions are met, you can catch Dusclops in the Dazzling Cave biome of the Grand Underground or with the Poke Radar on Route 224. You can also evolve a Duskull to obtain one.
Duskull can be found in the same Grand Underground biome from the very beginning of Pokemon Brilliant Diamond and Shining Pearl. It is also available on Route 224 via Poke Radar and evolves into Dusclops at level 37.
How to evolve Dusclops into Dusknoir
Dusclops can only evolve into Dusknoir when traded holding the Reaper Cloth. This means you need to find someone to trust to trade with in Pokemon Brilliant Diamond and Shining Pearl.
With the Reaper Cloth given to Dusclops, trade it with your friend. It will evolve into Dusknoir once your friend receives it. Then have your friend trade it back so the Dusknoir is yours.
Where to find the Reaper Cloth
You can find the Reaper Cloth on the ground of Route 229 in Pokemon Brilliant Diamond and Shining Pearl. Another method also requires you to beat the Elite Four and become the Champion. This will give you access to the Fight Area.
In the Fight Area, you will find the Battle Tower where you can battle here and earn Battle Points (BP) through certain streaks. Earn 5 BP and you can purchase the Reaper Cloth from the Battle Tower vendor.