This quest is not available in game.
Kill Scarlet Commander Mograine and High Inquisitor Whitemane.
Oh, it's great to see you again <name>! I'm afraid I'm going to need your help.
You see, Mograine's the Commander here along with High Inquisitor Whitemane, and they tried telling me that I wasn't really the new Scarlet Champion! 'Course, the boys and I didn't take kindly to that.
We're taking the Scarlet Monastery for our own and re-establishing the order as it always should have been - with me at the head of things! I'll take care of the Forsaken and the Scourge for good.
Help an old friend out?