This quest is not available in game.
Speak to Menara's acolytes inside the tower above Ratchet and choose one of their paths to follow.
Afterwards, bring an Infernal Orb to Tabetha in Dustwallow Marsh.
Good, then we shall begin.
The first thing you must do is speak to my acolytes inside. Choose one of their paths to follow--they will explain more.
Second, you must travel to Desolace and find an Infernal Orb from one of the warlocks of Mannoroc Coven. It is that orb that you will cleanse with the help of a mage named Tabetha deep in southern Dustwallow Marsh. She will aid you because of our history together.
Again, do not come back until you have done both things I've asked.