Azaloth can be found south side of the Black Temple. He's currently being held banished by several Sunfury blood elves. Players will need to kill Sunfury Warlocks or Summoners (not necessarily the ones holding Azaloth) until one drops a [Scroll of Demonic Unbanishing]. Use the scroll on the demon to release him. You do not need to defeat Azaloth, but he will attack you.
When released, he will go on a minor rampage and kill the warlocks that were holding him, until eventually Alandien comes over and kills him.
Description
The weapons are authentic, as we feared. Illidan is training demon hunters at the Ruins of Karabor and we must put an end to it.
Do not be fooled by their name, <name>, their power will be used against us as often as against any demon.
Their warlocks summon and subdue demons to be used as part of the initiates' training. A pit lord named Azaloth has proven too strong to be used in training and is kept banished. Find a way to let him loose on his captors. That should buy us the time we need.
Completion
Let us hope that distraction bought us the time we need to fully learn what we need of the training grounds at Karabor.