This quest is not available in game.
Purchase Xorothian Stardust from Ur'dan inside the Shadow Hold at Jaedenar in Felwood. Bring it to Gorzeeki Wildeyes in the Burning Steppes.
So you come to me seeking Xorothian stardust? You wish to open a portal to Xoroth, the domain of Hel'nurath my rival? Perhaps you plan to steal from him one of his precious dreadsteeds?
Very well. My servant Ur'dan has a supply of Xorothian stardust. You may obtain it from him... if you can pay the price.