DoF will feature, "creeps". I think I mentioned this on the RTSC forums, but when we first started making DoF, we had a big emphasis on making it so you could really make anything with the editor you wanted, and we planned to include tons of extra creatures and units for people to be able to make any type of scenario they wanted.
In DoF, "creeps" will be like Sharku suggested, they are neutral units that will attack anyone. They will be varied in power, and volume of units. It could be a group of highway men that hijack your patrols, or ferocious beasts in the forest.