Some of my counterparts have told me that the land wants to heal, but several high-ranking undead - along with the Cult of the Damned - are not allowing it to. That means we have to stop them! I've got a plan, but first, you're going to need a cultist disguise.
Head southeast into Corin's Crossing, and take the clothing from the human cultists that roam through the town. I'll contact you when you've completed this step.