A human skull painted with clown's make-up. It says it is searching for its body and lost memories.
The Heavy Skull is Skelly's head, and can be found in Fossil Valley (Another World). There, it made a ruckus by bellowing out and prompting the Acacia Dragoons to call in an exorcist (Greco, who they humorously turned away in favor of Serge's party).
From: Key Items (Chrono Cross)