A team-up with Eltariel, the elven ninja. Put Talion's keen forensics skills to work once more, and follow her trail.
You catch up with her just effortlessly busting Nazgul, because that's what elf ninjas do.
Still, slapping around Ringwraiths hasn't given her what she needed- you'll need to interrogate some worms in the nearby camp, with a bonus for stealth-dominating three archers.
It's much easier to do the archer objective first- so just skip from rooftop to rooftop until you have the requisite three (there are extras if your foot slips).
With that out of the way, dominate the worms. Nothing says you have to do this stealthily, so go at your own pace. Eltariel is certainly happy to cut down any orc you point her at as you make the rounds. When there's one Worm left, Eltariel will leave your side to deal with some incoming reinforcements. Dominate the last worm, then rejoin her.
You have an edifying conversation on ground saturated with orcblood, and the mission ends.