Hidden Potential of the Archmage

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.

Arcane
To obtain [item=139558] you need to:

• Polymorph following mobs:
  - Azsuna - [npc=89386]
  - Val'sharah [npc=109819]
  - Highmountain [npc=99636]
  - Stormheim [npc=107808]
  - Suramar [npc=110043]
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• Every day there is a chance [npc=111107] will spawn in Hall of the Guardian - when it does, right click it a few times and it will explode
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• Find [npc=111691] in Stormheim, right click it a few times and it will explode
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• Go to Tower of Azora in Elwynn Forest /way #37 63.8 68.4
• 
  
• Talk with [npc=111704] and complete a short event, where you'll need to kill some sheeps. After that kill [npc=111704] and then you can loot his corpse to get the [item=139558]
• 
  

Fire
[item=139559] has a chance to drop from mobs in Suramar.
A really good spot is near [npc=111649], there are many mobs in this area and they respawn fast.

Frost
[item=139560] has a daily chance to drop when using [order-advancement=386].
Speak with [npc=108331] and research [order-advancement=386] (second row, on the left). This will give you access to 5 portals that can take you to 5 Legion zones - you can find the portal on the lower level in the middle, in the hallway connecting east and west wings. Once a day, when using the portal, you have a chance to be teleported to Frostfire Ridge, where you can find [object=255953] - when you loot it, you will get [item=139560].

When I ported to my mage hall the first time for the day a message appeared: "You hear a strange crackling sound from the portals downstairs." Idk if this is the signal that the portals will send you to FFR, but I clicked the portal to Suramar and was ported there.

Same for me. I saw the message "You hear a strange crackling sound from the portals downstairs." in the chat and then clicked the Suramar portal and was ported there.