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 ) /waypoint -395, 12, -53. This step can only be done if you are level 66 or above, otherwise she will not speak with you.
She will send you to speak with Amares D'Venhz at the other end of the room ( -373, 12, -33 ) /waypoint -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:
Return to Amares D'Venhz ( -377, 12, -37 ) /waypoint -377.41, 12.20, -37.15. He sends you to find information about a relic or weapon suitable for ghoul hunting.
Note: The sub-quests are shareable, however each member must speak to Havras "Hack" Scutter for him/herself.
Also note: If you already have Ghoulbane he will offer both of these quests depending on your responses and it is possible to take (and complete) both of them even though only one of these is necessary to continue the HQ. Evil toons may wish to do Gogas' quest so as to bypass the hassle of sneaking into North Qeynos.
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 ( -380, -13, 141 ) /waypoint -380, -13, 141 near Freethinker 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./