Chief Engineer Copperclaw aboard Orgrim's Hammer wants you to throw a Writhing Mass into a cauldron at Aldur'thar.
Those twisted cultists are looking for souls to put in their crazy-juice? Then let's help 'em out a bit!
Take a swig of this - don't worry, I've diluted it plenty... I'm almost positive that its only effect will be to detect any cultist's essence.
Once you've collected a bunch of 'em, throw the writhing mass of twisted souls in one of their cauldrons.
Let's see how they like a taste of their own medicine!