WoW Transmog — Browse All Transmog Sets
Browse all 3,100+ World of Warcraft transmog appearance sets. Filter by expansion, armor type (Cloth, Leather, Mail, Plate, Cosmetic), and PvP sets. Track your wardrobe completion across all expansions.
Browse transmog sets from raids, dungeons, PvP, and quests across all expansions. Filter by armor type (plate, mail, leather, cloth) and source. Track which appearances you own and which you still need via Battle.net sync.
Attire of Piety
Cloth set. Mists of Pandaria. I'm very tempted to make a character named Abhorsen just so I can wear this.
Attire of Piety is a transmog set obtained from naval missions that reward Hellfire Citadel raid chests.
Unlock naval missions
Complete enough Hellfire Citadel raids on Normal and Heroic difficulty to unlock the corresponding naval missions; Normal missions require approximately 8 Normal HFC kills, while Heroic missions require approximately 12-15 Heroic HFC kills.
Complete naval missions
Complete the naval missions that reward 
Iron Fleet Treasure Chests containing Hellfire Citadel raid loot.
Open raid chests
Open the chests to receive armor pieces from Hellfire Citadel; note that chests do not contain set items, weapons, or class trinkets.