Simply head past the Sunspear Great Hall towards the river where the warthog is located. You may have to fight a Bladed Termite, and a Stormseed Jacaranda along the way, but it is not necessary for completion of this quest. Once you reach the warthog, Nehdukah will go about charming the beast, which may then spawn a group of Mandragor. Defeat the Mandragor and Nehdukah will complete his charming. Once done, simply lead him back to his friends and accept the reward.