In order to start the quest you must be able to speak Thulian.
Starting the Quest
This quest starts by speaking to Sinephobis at the very back of the temples on the Fear Tainted Isle in Tenebrous Tangle (take the cloud transport station found at the upper West side of the Temple Grounds island in Tenebrous Tangle - on the way to the Sanctum of the Scaleborn). When speaking to him, be subservient and give proper respect to the Priest of Fear. Do not try to bribe him.
To save time, pick up a (1) scintillating incense prior to starting the quest.
Harvest five dragon bone parts in The Bonemire and can only be seen if you are on this step of the quest. They spawn somewhere in the area of these locations and have a short (1-3 minute) respawn timer. A Gnomish Divining Rod can be used to save time in finding the nodes for this step (a pile of dragon bones). You can also use the tracker for harvestable items if you are over 90 in tradeskill and got it from traeskill prestige AA.
Dragon Ribs - Halls of Fate (Island), western-most isle (The Remnants of Xoch) ( 239, -355, 11 ) /waypoint 239, -355, 11
Return to Sinephobis and he will give you a recipe. He asks you to gather a few uncommon T7 harvests from any T7 zone (including Loping Plains). You can harvest them or buy them off the broker. If you have the items already you can place them in a sales display and remove them for the update. You can also have someone give you the items or have them traded back to you. The items you need are:
a blue-silver sheet from ore nodes (Kingdom of Sky zones: "firmament stone;" Loping Plains: "protruding vein")
You can use the Commission System for this step. If you use the Commission System for this be sure the person you are commissioning for uses their Instructions otherwise it will take your instructions.
When Do'ellin gets down to about 10% health, he will break the encounter and appear as an NPC, Do'ellin (with '<Subdued>' under his name). Target him and use the ornate phylactery to steal his soul. If you accidentally aggro the Subdued version, or he is up when you get there, killing him will cause Do'ellin the Young to spawn again.
Return to Sinephobis. He will hand you three rods and give you six minutes to place them around the islands in the zone.
You will need to find "a spot on the isle, away from any mobs, to use the rod". Many people experience issues with this step, which is often the most time consuming one. See Placing the Rods on the talk page for discussions on tricks people have tried to get this near-bugged portion of the quest to work.