Speak to Estulan.
Estulan, a powerful and uncorrupt Highborne, has managed to enter the western wing of Dire Maul and has asked for assistance in cleansing it. Regardless of your personal convictions of his kind, it is an effort I must support for our own good. Please hurry, we need every foothold in Feralas that we can get.
You will find Dire Maul to the west.