Prison of Planes on any Heroic Difficulty.
Get to the end of PoP where you fight the Warfoged named Cochitlehua. There are 2 standing there.
Talking to both activates both.
Both will drop the ancient docent.
One of the Cochitlehua were standing in the spot where the wraith stands in Epic difficulty.
I ran this 4 times each on Heroic C/N/H/E and all 4 times they were there.