This WoW set features the full Valorous Dreamwalker transmog, which is the druid tier 7.5 (25-man) raid set. Dreamwalker is obtained by looting Wrath of the Lich King bosses and purchasing some set pieces straight from the vendor with gold. Dropped tokens can be traded for set pieces via Dalaran tier vendors.
How to Get Druid Tier 7.5? By purchasing from vendors and slaying Naxxramas/Obsidian Sanctum bosses.
How Many Set Pieces?  Helmet, Shoulders, Chest, Hands, and Pants
Druid Tier 7.5 Transmog: [25-Man Drop Locations]
Note: Druids have three different sets with the same exact look. Tier 7.5 druid armor tokens can be used to purchase any of the set pieces.
Head: Helm of the Lost Vanquisher [Kel’Thuzad] in Naxxramas
Chest: Chestguard of the Lost Vanquisher [Gluth] in Naxxramas
Hands: Gloves of the Lost Vanquisher [Sartharion] in The Obsidian Sanctum
Legs: Leggings of the Lost Vanquisher [Purchase from Vendor] in Dalaran.
Shoulder/Leg Vendor (Alliance): Arcanist Ivrenne [37,55] in Dalaran.
Shoulder/Leg Vendor (Horde): Magistrix Lambriesse [65,23] in Dalaran.
Redeem Token Vendor (Both): Valerie Langrom [51,72] in Dalaran.
Set Name: Valorous Dreamwalker Battlegear (hover for set bonuses)
Shoulder: Valorous Dreamwalker Shoulderpads
Chest: Valorous Dreamwalker Raiments
Hands: Valorous Dreamwalker Handgrips
Legs: Valorous Dreamwalker Legguards
Set Name: Valorous Dreamwalker Garb (hover for set bonuses)
Shoulder: Valorous Dreamwalker Mantle
Chest: Valorous Dreamwalker Vestments
Hands: Valorous Dreamwalker Gloves
Legs: Valorous Dreamwalker Trousers