In Bloodscalp Clan Heads, you must defeat the chief and witchdoctor of the Bloodscalps and take their heads back to Grom'gol. This quest is in a long chain, all available in Grom'gol, the first being which can be obtained from Nimboya.
Bring and to the bubbling cauldron at the Grom'gol Base Camp.
You will need:
These two trolls can be found in the ruins in north-western Stranglethorn Vale, close to the beach. It is probably easiest to get to them from the beach side - just head as far north on the beach as you can and head up the ramps. The coordinates for Gan'zulah are [23, 8]. Nezzliok should be in the same area. If you can't find them at first just wait for a while, these two have very long respawn timers.
Turn in the quest at the Bubbling Cauldron next to Nimboya at the north entrance to Grom'gol Base Camp. After you turn it in, click on the cauldron again to receive the next two quests in the chain.
Yenniku was not among the heads, and I thank the Great Serpent for it. But we are no closer to finding him.
We must know the truth, and I fear that only the Bloodscalp chief and his witchdoctor know it. They are the enemies of the Darkspear tribe and will not speak freely, so we must force the truth from their dead lips!
Bring me the heads of Gan'zulah and Nezzliok the Dire and place them within this cauldron.
They are deep within Zul'Kunda. Bring their heads...we will then make them talk.
You will be rewarded with the following:
The greenish broth within the cauldron bubbles.
You place the heads of Gan'zulah and Nezzliok within the cauldron...