This quest is not available in game.
Speak to Ur'kyo in Orgrimmar.
One of your priests sent word to us that if we see you that we were to tell you to return to Orgrimmar, <name>. It seems one of your kind--a priest named Ur'kyo, if I'm not mistaken--believes you are ready for more training. It has to do with some of your cultures practices he said, and he wanted you to find this Ur'kyo in the Valley of Spirits.