Steal Silixiz's Tower Key from Foreman Silixiz, then kill two Mutated Venture Co. Drones, two Venture Co. Patrollers, and two Venture Co. Lookouts. Assassinate Grand Foreman Gallywix and take his head, then pick the lock on Gallywix's lockbox and steal the Cache of Zanzil's Altered Mixture. Take the Cache and Gallywix's Head back to Shenthul in Orgrimmar for further instruction.
You will need to steal the tower key from Foreman Silixiz, [player]. Once you've got the key in your possession, hold on to it - I may need it later.
Remember, the poison has weakened everything in this tower. Use your abilities to bring chaos and destruction to its inhabitants. Slay them all -- show no mercy!
Once everything inside lays in a bloodied heap, pick Gallywix's lockbox and steal the cache of Zanzil's mixture held inside. Take both the head of Gallywix and the mixture to Shenthul in Orgrimmar.