High Priestess MacDonnell: The last cauldron that remains is located on a farm now called Gahrron's Withering. It is guarded by some of the Scourge's tougher minions - specifically, wraiths and ghosts. They are not to be trifled with, Hacima.
Gahrron's Withering is due northeast of our position here, close to where the Eastern Plaguelands begin; again, eliminate the cauldron lord present there for its key. Here is your empty sample bottle; bring it to me filled. May the Light protect you in this dangerous mission, hunter.
Cauldron Lord Soulwrath: An access panel to the cauldron remains securely fastened. In order to open it, you will need to find the key.
Cauldron Lord Soulwrath: Cauldron Lord Soulwrath's key disintegrates as it touches the lock on the access panel at the base of the cauldron's platform. A slight clanking noise is heard within, and the access panel swings open to reveal more viscous toxins within the cauldron's framework.
There is a small spigot that the bottle fits well enough under, allowing you to draw a sample for Shadow Priestess Vandis back at the Bulwark.