Chestguard of the Lost Conqueror

Chestguard of the Lost Conqueror is a tier 7 armor token. It can be exchanged in Dalaran for the following items:
 * Heroes' Redemption Breastplate
 * Heroes' Redemption Chestpiece
 * Heroes' Redemption Tunic
 * Heroes' Robe of Faith
 * Heroes' Raiments of Faith
 * Heroes' Plagueheart Robe

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