The Draenei Prisoner can be found in Falcon Watch of Hellfire Peninsula. He's being held as a test subject by Apothecary Azethen.
At the completion of  Source of the Corruption the following event occurs:
- Apothecary Azethen says: ...a potent concoction!
- Apothecary Azethen says: But where could I ever find a suitable test subject?
- Draenei Prisoner says: [Draenei] X aman shi Sorankar Rikk ante il mishun il golad
- Apothecary Azethen says: Drink this, you blue brute! Disobey me and I promise you a slow, painful death!
- The draenei prisoner dies.
- Apothecary Azethen says: Hmmm... looks like I'm going to need a new test subject.
- Draenei Prisoner says says: I pity you Forsaken, your soul is devoid of light.