In order to end the Ango'rosh threat, we must kill their leader, Overlord Gorefist. We'll do better than that, though. We'll make an example of the overlord and his followers.
Go to the Ango'rosh Stronghold and deal with our foes. The stronghold is located in a cave on a small island to the northwest of Zabra'jin. You'll see a bridge made from a fallen mushroom beyond the Ango'rosh Camp.
Show no mercy, <name>. They certainly wouldn't spare any of us.