Obsidian Tie Event

Right now in season 2, you can earn this achievement by purchasing a full set of honor armor from Seltherex in Valdrakken's Gladiator's Refuge for honor. You can see the armor set under Primal Elements -> Aspirant (might be something else if you are alliance). If you buy a piece of honor armor you can click on the message in your chat to see the set.

Gotchas:

• 
  
• To make the achievement pop, you must equip each piece, such that they are no longer refundable.
• 
  
• If the pattern from previous expansions holds, once season 2 ends, this achievement will become unattainable until the next expansion, when this gear will be purchasable for Marks of Honor.
• 
  
• If you are looking to get easy honor, the Comp Stomp Brawl is a good choice, when it's active.
• 
  
• There's a bit of an oddity for leather-classes (and others?) where you may have collected the chest appearance from a different item prior to season 2, and so the chest armor tooltip doesn't claim it will give you an appearance, even though the chest won't be colored in on your set appearance tab. But, never fear, if you buy all the armor and equip it, the achievement will pop. (Good job Blizzard code!) I equipped and bought the chestpiece last, don't know if it matters.
• 
  

Does anybody know if this can be obtained by buying the gear set for honor?
Edit: I can confirm the comments below that you can get it from buuying the honor set "Obsidian Aspirant". Make sure you buy the correct cloak like the below comment says.
After you have bought the gear, you need to equip it or wait until it is no longer refundable to obtain the achievement!

You can earn this achievement by buying the Honor Point gear. Make sure to buy the correct cloak to complete the set. For Warrior, greatcloak was the back variant listed in the set tab to finish it.