This quest begins by clicking on the bottle located at 58.01, 210.29, -34.11 Note: Clicking this bottle also updates the quest "The Tower of Frozen Shadow" for the step "Find a way to weaken Vethilot". This will only work if the quest "A Ruinous Bath" isn't already completed for the zone or if you already have it in your journal.
Once you have the quest you will need to collect 3 potions by completing the quest: A Ruinous Bath
After you complete A Ruinous Bath you will have a new potion in your inventory called The Collected Potions. Pouring this in the pool will spawn Vethilot the Corpsemonger.
Position your group AWAY from the pool and have them stand in a tight group but NOT in a corner.
Have one of your group members poor the potion in the pool located at 62.00, 209.00, 5.00 then step away from the pool.
After a few minutes Vethilot the Young will walk down the hall and enter the pool. When he does he will be transformed into Vethilot the Corpsemonger and become attackable.
As you fight him Skeletons will spawn, depending on your gear you can ignore them and let your AOE's kill them, mez them or attack and kill them as they spawn.
When you kill them you have 5 seconds to double click on their bodies to destroy them or Vethilot the Corpsemonger will warp to the body and begin to buff himself. If he gets to many buffs you will not be able to kill him. This is why you do not want to be in a corner or in the pool when you fight him as it will make destroying the bodies very difficult. He will also suck buffs from any group members that die so ensure no one dies. Every dead body he is able to suck from adds another buff of Corpsemongering to his list of buffs and they will keep stacking.
Strategy Epic x2
Same as above except he will be standing in the Sergeant Schriber room.
Increase INT of target by 25.5
Increase Multi Attack Chance of Target by 3.0
Increase Mitigation of target vs elemental, noxious and arcane damage by 158
Heals target for 0.0% of max health
Increases Crit Change of target by 2.0
Increases Crit Bonus of target by 2.0%
Increases Damage Per Second of target by 50
Increases Attack Speed of Target by 50
Increases Focus of target by 8.5
Increases Mitigation of target vs physical damage by 158