Beyond the Sands - Chapter 4

Our pathetic kin thought to take a defensive position atop that hill to stop our advance. They are trying to protect the Threshold to the Isle of the Dead long enough for some pathetic ritual to take place. They think they can stop us... they do not grasp what control we have over the Winds of Magic. Any spells they weave to ward the Vortex will be undone by us, at Malekith's will of course. As for your relic, what they planned on doing with it is uncertain. Possibly destroy it using the magical powers of the Isle. It is not here, but you are, and while you are here you will help us secure the Isle of the Dead by corrupting its rituals. Then you can look for your chest. I'd be willing to bet my life that it'll be empty of anything of value.

Travel to the Isle of the Dead and complete the four rituals there, that is the Rituals of Shadow, Metal, Fire, and Light. Afterwards find the Nehekharan Artifact on the hill east of Saruthil's Wake.