wearing Pelagius' clavicle-bone as a mask, to the Mad God's Masque Bellicose Ball?

It was our literal skeleton key into the mind of a horker. That's what a Pelagius is: a sea-dweller. No wonder he was "insane". What would you do, if Clavicus Vile mixed your brains with a walrus, as a token to his big brother "Sheggars"?

Not rule an Empire well.

Pretty sure it was the pelvic bone, not the clavicle. I'm not sure I would want Pelagius' crotch on my face, though.