Chronicles of the Spellhammer Grimiore
Mysterious Crystal Skull
This mysterious crystal skull is characterized by a vertical crack on the back of it. Dark purple energy pours out of the back of this gaping wound, and whoever looks into the crack witnesses unfathomable horrors.
Recently the party discovered that this energy provided a dark aura around the area of whomever holds it, which incidentally protects a group from any scrying techniques.