Where would the ghoulish army come from?
I'm thinking they'll eradicate Nargothrond from most of the story. Maybe Beren would pass there and encounter the shade of Orodreth (unnamed, of course), and some Mr. Obvious (Mablung or Beleg, you choose--well, Mablung sounds unelvish, so he'll become a Dwarf. Three hunters!) will tell the Dwarf that Beren's forefather cursed the dwellers of Nargothrond because they refused to fight.
Whew! Or maybe the ghoulish army would come from Nan Dungortheb . . . all those victims of the spiders . . .