This quest is acquired upon finding a scroll in The Wounded Coast. The scroll is on the ground near a corpse, located south of the area's entrance at the end of the first dead end path. (see map, below).
The journal will update, telling you that a new hidden lair was discovered. Travel towards 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.
The formula for Fell Grenade can be found inside a crate upon the nearby inlet (by the marked location, not the scroll's location).
After killing Medan, your journal will update stating you have completed the quest.
RewardsGirdle of the Elders
+8% healing to this character
+3% damage resistance, a belt dropped by Medan
- If you loot The Awiergan Scrolls: First Aspect last, the passage near Anders' Clinic involved in Pride Unbound will still open.