Find someone that can tell you about the tattooed flesh. Talk to Tavish Dracinov in D'Venhz Rectory in the Village of Somborn in Loping Plains ( -395, 12, -53 ). This step can only be done if you are level 66 or above, otherwise she will ignore you.
She will send you to speak with Amares D'Venhz at the other end of the room ( -373, 12, -33 ).
He tells you that the symbol is the glyph of Mordiggian, a cannibalistic creature that stalks the Loping Plains, and he sends you to gather:
Kill Mordiggian, 68^^^ Heroic mob in the Breathless Hollow area of Loping Plains. To spawn him you will examine what looks like a plate on a rock near Freethinkers Hideout. He will have 3 waves of adds. When the adds pop, he depops and seems to respawn back at the plate. The adds are a separate encounter.
Return to Amares D'Venhz in the chapel to claim your reward.