How to Get the Mallet of Zul’Farrak
In Zul’Farrak, you will need the “Mallet of Zul’Farrak” to summon one of the bosses, Gahz’rilla. They cannot be summoned otherwise.
To obtain the mallet you must kill Qiaga the Keeper on the Altar of Zul in The Hinterlands and loot her mallet. You must then use the mallet you looted on the altar on the top level of Jintha’Alor in the Hinterlands and it will turn into the Mallet of Zul’Farrak.