Find the clue by opening a box and receiving Spectacles of Anti-Obfuscation in the Hall of Necromancy in Paineel at ( 1663, -267, 3175 ) /waypoint 1663, -267, 3175. Equip the spectacles and then read the note on another table in the same room at ( 1657, -267, 3195 ) /waypoint 1657, -267, 3195.
Speak to Arzachel and give him the item you have chosen.
This part is 2 updates! Make sure you complete whole dialog with Arzachel.
Kill Dread Exarch Mordek in Befallen: Necrotic Asylum and examine the book you loot from the body. You must be in the zone while examining the book to get the update, and you must do the L90+ version of the zone to get the book to drop.
Note: The update by examining the book worked for me even outside the zone. (26 Feb 2016)
Butrus is found in the far northeast corner of Toxxulia's Reach, at ( -60, 126, 2783 ) /waypoint -60, 126, 2783. Click the corpse to get your update. You will receive a book Diary of Butrus.
Investigate the Sepulcher outside Windstalker Village in Antonica ( -1747, -13, -714 ) /waypoint -1747, -13, -714. Enter The False Sepulchre and defeat the defenders. There will be groups of skeletons all around the room, and a pair of named bone Roper models guarding the chest.
After killing the four groups of Heroic level 93^ skeletons (linked groups of three) - the two ropers become attackable, linked level 94^^ heroics (Cranioxyth, Fibrodysaith). Very hard to solo the roper pair, best to get some help in order to survive. The ropers have a lot of hitpoints and each has a melee AE attack.
Open the chest to receive your reward. Make sure you don't have "The History of Gynok Moltor" in your inventory already, or the chest will be empty for you.