Gather Witherbark Skulls and place on Nimboya's Pike. Place Nimboya's Laden Pike at one of the Witherbark Villages in the Hinterlands, then return to Nimboya in Stranglethorn.
The Witherbark trolls were once allies to the Horde, but they betrayed Thrall... and that must be punished!
Here, take my pike and go to the Hinterlands, far to the north. You will find it northeast of Tarren Mill, a village held by our allies, the Forsaken.
When you enter the Hinterlands, hunt Witherbark trolls. Gather their skulls and drive my pike into the ground at one of their smaller villages, Hiri'watha or Zun'watha.
Show them their vile actions are of consequence!