What are the dark Pokemon in diamond?

There's no such thing as "dark Pokemon" in the sense of a specific type of Pokemon being inherently dark. In the Pokemon world, "Dark" is a type, like Fire, Water, or Grass.

Here's what you might be looking for:

Dark-type Pokemon in Diamond:

* Houndoom: A Fire/Dark type, found in the Grand Underground.

* Absol: A Dark type, found in the Grand Underground.

* Purugly: A Normal type, but it learns some dark type moves. It can be found in the Grand Underground.

* Weavile: A Dark/Ice type, evolved from Sneasel. It can be found in the Grand Underground.

* Garchomp: A Dragon/Ground type, but it learns some dark type moves. It can be found in the Grand Underground.

* Crobat: A Poison/Flying type, but it learns some dark type moves. It can be found in the Grand Underground.

Other Pokemon that might be considered "dark" in appearance or lore:

* Giratina: A Ghost/Dragon type, said to be a Pokemon of the anti-matter dimension. Found in the Distortion World.

* Spiritomb: A Ghost/Dark type, found by collecting 107 wisps.

* Darkrai: A Dark type, which is a legendary Pokemon. It is found in the Fullmoon Island.

Important Note: The Grand Underground is a location in Pokemon Diamond where you can find many different types of Pokemon, including Dark types.

If you're looking for a specific type of Pokemon, you can use the Pokedex or online resources like Serebii.net to find out where they are located.