The demon Mephistroth is one of the most powerful of the Nathrezim--the dreadlords. I can see in your eyes that you know what I am going to ask you to do. But it is for your own good! You can't keep wandering the lands looking like you do.
Most recently, Mephistroth has been dispatched by the Legion to the Cathedral of Eternal Night. No doubt, he will be wearing some legplates that I believe contain Wardenscale. Take them, shine them up, and bring them to me.