Cruel Intentions

These sets are part of Cruel Intentions, Legion season 3 & 4 (overall season 21 & 22).
Purchasable from Leutnant Surtees (A) and Apothecary Lee (H), Dalaran/Legion:

1. 
   
2. [class=6]: [transmog-set=2366] (A) / [transmog-set=2367] (H)
3. Death Knight
   
4. [class=12]: [transmog-set=2348] (A) / [transmog-set=2349] (H)
5. Demon Hunter
   
6. [class=11]: [transmog-set=2351] (A) / [transmog-set=2352] (H)
7. Druid
   
8. [class=3]: [transmog-set=2360] (A) / [transmog-set=2361] (H)
9. Hunter
   
10. [class=8]: [transmog-set=2339] (A) / [transmog-set=2340] (H)
11. Mage
    
12. [class=10]: [transmog-set=2354] (A) / [transmog-set=2355] (H)
13. Monk
    
14. [class=2]: [transmog-set=2369] (A) / [transmog-set=2370] (H)
15. Paladin
    
16. [class=5]: [transmog-set=2342] (A) / [transmog-set=2343] (H)
17. Priest
    
18. [class=4]: [transmog-set=2357] (A) / [transmog-set=2358] (H)
19. Rogue
    
20. [class=7]: [transmog-set=2363] (A) / [transmog-set=2364] (H)
21. Shaman
    
22. [class=9]: [transmog-set=2345] (A) / [transmog-set=2346] (H)
23. Warlock
    
24. [class=1]: [transmog-set=2372] (A) / [transmog-set=2373] (H)
25. Warrior
    

---

Price:

• 
  
• 1 Ensemble costs 12x [item=137642]
• 
  

They only sell the ensembles, no single items. You don't need a pvp rank to purchase the ensembles.

---

Achievements for PvP-Appearences:

• 
  
• Season 1: The Original (BC)
• 
  
• Season 2: No Mercy (BC)
• 
  
• Season 3: With a Vengeance (BC)
• 
  
• Season 4: Tough Threads (BC)
• 
  
• Season 5: Lethal Looks (Northrend)
• 
  
• Season 6: The Fierce and the Furious (Northrend)
• 
  
• Season 7: Relentlessly Good Looking (Northrend)
• 
  
• Season 8: Wrath of the Stitch King (Northrend)
• 
  
• Season 9: Viciously Vintage (Cata)
• 
  
• Season 10: (Ruth)less is More (Cata)
• 
  
• Season 11: Cataclysmic Catwalk (Cata)
• 
  
• Season 12: Why Male(volent) Models? (MoP)
• 
  
• Season 13: Dressed to Oppress (MoP)
• 
  
• Season 14: It's Not Fashion Unless It Hurts (MoP)
• 
  
• Season 15: Wear It With Pride (Draenor)
• 
  
• Season 16: Untamed Beauty (Draenor)
• 
  
• Season 17: Wild Style (Draenor)
• 
  
• Season 18: War-Mog-ering (Draenor)
• 
  
• Season 19 or 20: More Like Win-dictive (Legion)
• 
  
• Season 21 or 22: Cruel Intentions (Legion) (you are here)
• 
  
• Season 23, 24, 25: Claws Out (Legion)
• 
  

The sets you want for this achievement are the sets from Legion season 3 and 4.

From the guide:

This new PvP style will be introduced in Patch 7.2. At first, you will have to acquire all of the pieces via strongboxes from participating in Legion PvP. Vendors that sell these items for Mark of Honor will be available when Legion Season 5 starts.

Update: Since season 3 & 4 are now over you will want to visit [npc=106930] in Greyfang Enclave if you are Alliance or [npc=119486] if you are Horde

You obtain these by obliterating current Season Gladiator (epic) PvP gear at the Obliterum Forge in Dalaran. If you obliterate Elite gear, you get Echoes of Domination instead. Rare quality "honor" gear cannot be obliterated. Jewelry can be obliterated while Relics can not.

You can turn in 75 Echoes of Battle for a Gladiator armor token of your choice to Marshal Frazer in Greyfang Enclave (Alliance) or Violet Shadowmend in Windrunner’s Sanctuary (Horde) in Dalaran.

There are no tokens for jewelry or trinkets, only armor pieces.