I want it for my Roserade so he will be immune to the sand storm damage(sorta). I am not going to use Leftovers becuase that is for my Umbreon.
In platinum, you can find the Black Sludge On Wild Croagunk and Wild Toxicroak. If you have HG/SS, you can find it in Cerulean Cave, and on Koga's Muk, but you'll need some other way of stealing it, because I think it has the ability Sticky Hold.
