Shadowguard
Speak to Ur'kyo in Orgrimmar.
Description
Something important is up in Orgrimmar, <name>.
The normal messengers that come through here looking for troll priests usually are very casual. This time, they seemed to be in much more a hurry. Don't dally too long in Thunder Bluff. I'd return to the Valley of Spirits as soon as possible.
Completion
Your rites will come soon enough. For now, I teach you a spell that will be of great use to you when you do battle with your enemies.
Rewards
You will learn: 
Shadowguard (Rank 1)