Oazduke's Vengeful Head.
The head haunts all headsman and executioners.
A floating, bloody head, long separated from its body, is a particular legend among a very particular group of people, executioners, specifically those that chop heads from a block for a living. It was that infamous highway robber, Oazduke the Vengeful, who when finally captured and put to the axe, screamed his foul hex, seconds before his head flew off.
"You will know it is me when I'm through
A curse on your ilk and on you!
May my severed head haunt you eternal
Frightening you headsmen infernal!"
Years later, not one but two(!) weary, puffy-eyed, spooked, headsmen, haunted day and night by Oazduke's insufferable severed head, approach the party cleric in order to hire him to exorcise the ghost head once and for all.