As ramolnar suggested,
Evil Smelling Fens could be a good choice for you, but only if you decide to go with
Plotting Deceiver.
Dark as Darkness already exerts himself so you don't get the full potential.
Also, when I was building Morgul Archery deck, I also used 2-3 copies of
Morgul Creeper. Since I always prefer a Shadow Kill over Fellowship win, I often bid 0 and let people go first (this has also been the cause of my many losses, but those wins make up for it). Many players will bid 1 to go first. I just used
Pelennor Flat* which provided a win-win situation -> 2 burdens or initiative. I also run
Northern Ithilien and you'd be amazed how many times I managed to corrupt my opponent with my Morgul Archery deck.
If you won't run
Morgul Creeper then take
Steward's Tomb as your site 5. It's a good site even for your freeps.