In the west region of the valley there is a cave with a necromant (near the cave is a teleport shrine). You have to find a crystal skull for him which you can find in a cave southwest in the valley, where a hurted man lies in a camp infront of the cave.
Bring the skull to the necromant to end the quest. Then go to your inventory quest items and select the skull and use it. Make sure that you have some bodyparts which you have to put together for the necromant. You can always change the bodyparts to create your favourite creature.