Enter the Den of the Devourer and kill the ten books. These are invisible, so you'll need some sort of see-invisible ability to be able to see them. (It's possible to hit the invisible books with blue area-of-effect spells, such as healer de-aggros). IMPORTANT! Make sure to destroy all ten books before killing The Devourer since you will need that mob after killing all the books
Volume I - first Hallway, second to last set of bones. (Visible)
Volume II - Room at end of first hallway. (invisible)
Volume III - Room at end of first hallway. (invisible)
Volume IV - Third set of bones in north hallway off Volume II and III's room. (Visible)
Volume V - In the room at the end of north hallway around (invisible) ( -330, -43, -61 ) /waypoint -330, -43, -61.
Volume VI - Down south hallway of Volume V's room. Second set of bones around ( -303, -40, 6 ) /waypoint -303, -40, 6. (There have been reports of another copy in the named ring event's room.) (invisible)
Volume VII - Hallway to Water spirit room (Visible)
Volume VIII - Water Spirit Room (invisible)
Volume IX - Final room entrance alcove (invisible)
Volume X - In the alcove behind Devourer (or in the alcove below). REMEMBER: Pull the book first, then kill the Devourer. (Visible)
The Acrid Mother or her placeholder, an acrid maiden on Ravasect Isle. She roams around ( 930, -120, 280 ) /waypoint 930, -120, 280. Find these in a 3-member group that includes 2 beetle mobs (level 71^ Solo).
The Humator Harridan (level 70^ heroic) on Ravasect Isle, down the tunnel at ( 980, -100, 170 ) /waypoint 980, -100, 170.
The Carnovingian (level 70^^ heroic) or its placeholder, a carnoligian, a timed spawn in Carrion Briar, around ( -140, -70, -520 ) /waypoint -140, -70, -520.
The Carrion Mandragora (level 72^^^ heroic) or its placeholder, a carrion mandrake, in Carrion Briar, down the underwater tunnel at ( -240, -80, -450 ) /waypoint -240, -80, -450. Note that the placeholder typically spawns at nearby at ( -200, -146, -390 ) /waypoint -200, -146, -390.
Haraghur the Deathless (level 70^^^ heroic) in Cacotoxic Stain at ( 240, 230, -710 ) /waypoint 240, 230, -710.
Examine "The Crystal of Drukaunis" you received earlier from killing the Devourer.