How to Get Mallet of Zul’Farrak
Mallet of Zul’Farrak is used to summon Gahz’rilla in Zul’Farrak.
You obtain the mallet by killing Qiaga the Keeper atop the Altar of Zul in The Hinterlands and looting her Sacred Mallet. After doing so, you need to ride to the top level of Jintha’Alor, also in Hinterlands, and use the Sacred Mallet at the altar located there. This will form the Mallet of Zul’Farrak.