Breastplate of the Lost Conqueror is a tier 7 armor token. It can be exchanged in Dalaran for the following items:
This item can be found inside the Four Horsemen Chest after defeating the Four Horsemen in the 25-man version of Naxxramas. It can also drop from Gluth.
[Chestguard of the Lost Conqueror]
/ Patch 3.0.2 (14-Oct-2008): Added.