Tar Goroth may be dealt with, but his summoner Zog is still at large. Return to Carnan for counsel.
As a side note, it's interesting that Carnan seems to be the only entity in the game that Cel truly honors and reveres- a more Machivellian Bright Lord might take this opportunity to enslave her while she's weak. Is it his elven upbringing, or his belief that Carnan would never oppose his rule?
Either way, your goal is to find the source of stench afflicting the land. You can follow the trail, or just head toward the yellow objective marker.
This will lead you to a formerly dead orc, now termed a revenant. Still, he can be defeated like any other grunt.
There are three more like him up the road, ripe for a chainkill, or whichever means you prefer for taking down no-names.
This will give you an objective for the source of the dark energies hereabouts, and it does look nicely bleak.
Cel will point out that the necromantic totem here must be destroyed. There are quite a few revenants milling around it, as well as Zog himself, so you may wish to secure a tactical advantage by scaling the nearby tower first, and attacking from the air. Killing won't keep them down permanently, but it's an effective delaying tactic.
Still, your primary goal is take out the totem. Unlike the tribal totems you've seen before, you do not need to scale this one and knock off the top- just hold down E as if for a domination. This does take some time, so you may want to lead the revenants on a ring-around-the-rosy about the tower to buy some breathing room.
Now you can turn your full attention to destroying your foes.
Zog escapes again, but the mission completes once his minions have been accounted for.
