The complete Pokemon Diamond and Pearl pokedex, part 9

Pokémon Name: Dusknoir
Type: Ghost
Classification: Grab
Pokédex Number: 477 National
Ability: Pressure – Opponent uses two PP with every attack
Useful Attacks: Payback
Location Found:
D/P/P/HG/SS: Evolve from Dusclops via trading while holding the Reaper Cloth
B/W: Poke Transfer

One of the more popular Pokémon in Pokémon Ruby and Sapphire was Duskull and its evolution Dusclops. Leveraging that popularity and responding to the relative lack of three-tier Ghost Pokémon, Gamefreak created this evolution. Dusknoir carries the souls of the dead to the afterlife, and every once in a while they leave a scrap of cloth from the spirit world in the world of the living. If a Dusclops holds this otherworldly textile and is sent through the ether via a Pokémon trade, it'll evolve into Dusknoir. Dusknoir doesn't learn many moves over its predecessor, but its stats are a definite improvement.