Warbringer Battle-Helm

The Warbringer Battle-Helm is the Tier 4 plate head armor for offensive Fury or Arms warriors and gives bonuses to strength, agility, stamina and overall offense. It is available through token item that drops in Karazhan.

Source
This item is sold by in the Seer's Library on the Scryer's Tier and by  in the Shrine of Unending Light on Aldor Rise in Shattrath City. The cost of the item is a token.