You did listen to the cannibals, right?
You might either want to talk to the cannibals again or reread your memos for a refresher.
LeChuck stole the cannibal's voodoo antiroot.
With this antiroot, the Cannibals can make a potion to destroy ghosts.
You have to return the voodoo antiroot to the cannibals.
How do I get the voodoo antiroot?