Hidden Potential of the Grandmaster

To complete this achievement, you need to unlock one hidden appearance for your class. To be able to get a hidden appearance, you need to have the class hall unlocked and the base artifact for your spec.

Brewmaster
[item=139561] has a daily chance to drop from [object=253076]. The keg is located in Monk Class Hall, inside the building behind [npc=101749], and to access it, you need [order-advancement=254] class hall upgrade.

Mistweaver
[item=139562] has a chance to drop from [npc=102679] (Dragons of Nightmare) in The Emerald Nightmare (any difficulty).

Windwalker
[item=139563] has a chance to drop from the Withered Army Training. It is speculated that you need to reach a score above 300 to have the chance to get the appearance.
To unlock Withered Army Training, you need to do the Suramar campaign until you get a quest Building an Army, and after you complete it, you will have Withered Army Training unlocked.

To get the "Legend of the Monkey King", u don't need to be spec'd as brewmaster to get this from the bubbling keg, i got the item on my windwalker monk - however, u do need to spec into brewmaster to collect the appearance.

Raynne, set loot spec to the appearance you're after. It worked on my ret pally when farming the holy appearance.