The Perfect Poison

My brother and I run the poison operations out of the manor Ravenholdt. Lord Ravenholdt tasked me to track down a new and extremely effective poison compound that can be crafted from the venom sacs of the inhabitants of Zul'Gurub and the Ruins of Ahn'Qiraj. There are two particularly venomous beasts residing in those blasted ruins that possess what it is that we might be looking for, <class>. Bring me a venom sac from the beasts Kurinnaxx and Venoxis and we would be eternally grateful.