According to Sselnyl Do'Zyth, there are a number of roused spirits at the Wellspring of Nightmares, east of Hate's Envy. Sselnyl wants me to take care of the spirits and then toss the vex-runed remains of the Dragoon-General inside the Well to disrupt a Thexian ritual. Once I've succeeded, I am to report to Ginwyss D'Arkenett. I can find Ginwyss stationed at T'Vatar Post, which can be reached by following the road east out of Hate's Envy.