I smell their cauldrons from here, but that's not plague they're cooking.
Pledges to the cult are forced to drink a concoction that steals their will and enslaves them forever to the Lich King.
Some say the potion contains the twisted soul of a being who was tormented before being mercilessly slaughtered, but I've never been able to reproduce it...
Fill this flask with a sample from each of the three cauldrons in the northwest region of the gate and bring it to Chief Engineer Boltwrench.
Whatdya got there, <race>?
<Boltwrench pours the contents of the flask into his tetrahydroparticle analyzer.>
What we have here is a simple failure to conglomerate...
There is a slight Easter Egg in this quest. The terms "Cannot Reproduce", "Not a Bug" and "Need More Info" are terms used for "states" of a bug tracked in the program "DevTrack", which is used by Quality Assurance Testers and developers to communicate about bugs written up by the testers. Therefore this is a slight homage to QA Testers throughout the game industry.