Seek out and slay Painmistress Gabrissa at Illidari Point and return to the corpse of Ar'tor, Son of Oronok with the Crystalline Key.
Painmistress Gabrissa is located just up the steps to the west of Ar'tor's body [28, 47].
Painmistess Gabrissa is a level 70 demon and is relatively easy to kill.
From assessing the scene, you note that Ar'tor is being held in place by energy beams emanating from the crystals hovering around the rune. Try as you might, Ar'tor is unmovable.
You note that the crystals have an empty slot at their base - perhaps for a key. It also seems as if succubi periodically perform some sort of ritual at the site.
Search Illidari Point for their leader. Perhaps she holds the key to releasing Ar'tor.
Ar'tor hovers lifelessly before you.
You slide the crystalline key into the slots at the base of each of the demonic crystals.
-  / 
- This opens up the search for the three parts of the key.
- [70 G5]