It's a Pagan artefact. No one really knows what it was or was made for, though it was apparently used as a weapon at one point. I stole it at one point for a rich buyer called Constantine. He told me it was a gem. I started to doubt that when the damn thing spoke to me and told me how to get to it. Then after I got it, Constantine had Viktoria rip one of my eyes out to power the Eye.