Read the Tainted Parchment and speak to Nartok inside the Den in the Valley of Trials.
Ah, while you were gone a parchment came for you, <name>.
I usually avoid dealing with warlocks if I can help it, but I think you should read it when you have time. If I'm not mistaken, it came from your newly-appointed trainer Nartok. He would have words with you when you're ready.
And now you've joined our ranks also. Don't misunderstand, <name>. Just because you have access to power that many will be jealous of, it does not mean you will be accepted easily. Thrall allows our kind into Orgrimmar because we are still his fellow kin--he cannot turn his back on us, or we would become as pathetic as the humans who enslaved him. My point is: be careful. You can be powerful, but if you are foolish, then you are as good dead.
If you need training in spells then return to me.
Upon completion of this quest you will gain:
The entirety of this quest happens at Durotar