This quest is not available in game.
Report to Gakin the Darkbinder in the Mage Quarter of Stormwind.
Isn't that how it always works? Was looking for you all day and couldn't find you, now when I'm not expecting it, you come and walk right up to me.
I've wasted enough time trying to find you, so I won't delay you any longer. Master Gakin's summoned you for additional training. Seems to me you should seek him out as soon as possible.
You'll find him in the basement of the Slaughtered Lamb tavern. By the way, you might want to keep that particular location quiet. Don't want word spreading about it.