After taking the camp, Arvaethor has asked you to follow him into the maw of the mountain and stop the source of the monsters descending into the Vale.
'The Orc cavern we entered on the eastern slope seemed to delve deep into the mountain. This crevasse may contain passage to the other encampment.
'You have done much and we have made it this far. I shall enter the mountain before you and scout out the passage. Enter after I do and make sure you are not followed. We shall meet up again shortly.'
The western entrance to Nimrond is located atop the mountain encampment of Dâr Matum.
Enter the western side of the Nimrond caverns.
Arvaethor is located somewhere in the caverns of Nimrond.
Search deeper into the caverns of Nimrond for Arvaethor.