You have to evolve it from duskull. Then you evolve it into dusknoir using a reaper cloth. You have to trade it while duskclops is holding it. You can find a reapercloth in a house at Iron island once you obtain the National Pokedex. To get to Iron island you go to canlave city and talk to the sailor on the other side of the dock. Ofcourse you have to have Pokemon Pearl, Diamond, or Platnem.
what you do is import it from ruby or Sapphire after you beat the game.
Give it a reaper cloth and trade it.
you can find duskclops in the tower where rayquaza is.
I think after you get out of Distorion World you should end up in Spring Path.There is some grass around the place.I would say look in the grass,I have seen some Duskclops in that grass
Let it hold a reaper cloth (maybe its called dark cloth) and trade.
go to the Forest that connects the mansion then catch all the duskclops
You need to find the Reapers Cloth around Lake Aucity or the Resort Area and trade it.
its not an emerald its RAYQUAZA the main legendary Pokemon in Pokemon emerald.
You cannot get a Yanma in Pokemon Emerald, as only Hoenn Region Pokemon can be found in Pokemon Emerald.
There is no PalPark in Pokemon Emerald.
Sinnoh Pokemon DO NOT EXIST IN EMERALD!!!
There is no Autosave in Pokemon Emerald.