Vereth the Cunning at the Rise of Suffering wants you to use a Lithe Stalker's heave ability to destroy 12 sleeping Iceskin Sentries.
12x Iceskin Sentry destroyed
Gargoyles make effective scouts and can be deadly if left to rain attacks from the air, but they have a very obvious weakness. Most of them have to go through long periods resting as stone to maintain the energy they need to carry their heavy bodies through the air.
As I peered through the eye you were using, I noticed dozens of iceskin sentries resting on the eastern and southern walls inside. Use the stalker to leap up to their ledges and devastate them while they sleep.