You must survive the Mooh'Tah Master for two minutes. He can't be killed, and you can't leave the arena before the time of 2 minutes.
Zao, in a small enclosed arena at the center of the orc camp.
Never stand in front of it, always be at an angle and at least 2 sqm away from it. Very easy to survive for 2 minutes, all vocations just run from it and use Light Healing when you get paralyzed. You can do the mission at as low level as 50