Here you and the elves journey to Cirith Ungol to stop the creation of more Chosen.
Your secondary object here is to stealth dominate three archers. Do that first, as it'll be much harder once the screaming starts.
There are plenty of archers here, so if you do accidentally alert one, kill him instantly, and then use Wraith Vision to locate another likely target. When you're done with that, it's Ritual Disrupting time. All the enemies will make their introductions, but stick with the plan here and focus all your attention on the Nazgul. Unlike, Helm Hammerhand, this one uses the normal teleport-strike, which you can use to lure him far away from his allies, where you can take him apart undisturbed.
That leaves the three Chosen captains, but their choseness hasn't made them especially formidable or given them any new powers. Dispose of them as you would any other captains.
When all have been accounted for, the mission completes.