Chestguard of the Lost Vanquisher

Chestguard of the Lost Vanquisher is a tier 7 armor token. It can be exchanged in Dalaran for the following items:
 * Heroes' Bonescythe Breastplate
 * Heroes' Scourgeborne Battleplate
 * Heroes' Scourgeborne Chestguard
 * Heroes' Frostfire Robe
 * Heroes' Dreamwalker Raiments
 * Heroes' Dreamwalker Robe
 * Heroes' Dreamwalker Vestments

Source
This item can be found inside the Four Horsemen Chest after defeating the Four Horsemen in the 10-man version of Naxxramas. It can also drop from Gluth.

This item is also sold by the following vendors for :
 * in Dalaran
 * in Dalaran