Acquisition
The Awiergan Scrolls: First Aspect is acquired upon finding the scroll in The Wounded Coast during Act 3.
Walkthrough
After reaching The Wounded Coast, head south from the entrance to the first dead end path. It is next to a corpse found at the end. Your journal will update telling you that a new Hidden Lair has opened. The Hidden Lair can be found in the middle of the map, just to the south of the Tal-Vashoth camp. From the entrance to The Wounded Coast, go left, following the path, taking your second path on the right. You will know you have reached the right area when you see an X on the map, and you are attacked by several mobs of undead and finally an Arcane Horror named Medan. Contrary to the journal entry, you'll be attacked in a clearing; you don't enter a cave or any sort of special map.
If you are still having problems finding the lair, try taking the 2nd right from the entrance on the southern path.
Result
After killing Medan, your journal will update stating you have completed the quest.
If you loot The Awiergan scrolls: First Aspect Last the passage at Anders clinic will still open.
Rewards
Medan drops Girdle of the Elders, a belt.