"Ah, yes. It is as I feared, Guardian. The skull you retrieved is one that is often kept by the followers of a powerful undead sorcerer, named Scorpio. You'll likely find him in the very depths of that place. I would not take Scorpio lightly, Guardian. He is very powerful. If you have any allies you can bring, make sure you do. Return to the Burial Grounds, and find and kill Scorpio."