—Information accurate as of: build 904.83
The Human Skull is a resource item that is obtained by harvesting the resources from a player's corpse by smashing it with a tool. One human corpse usually provides one Human Skull. Currently they have no practical use, except they can be smashed in the inventory screen by clicking on the item and choosing "Crush". This will yield 20 Bone Fragments.
This is also a component required to craft the Skull Fire Pit (Special halloween edition of fireplace) with 100 Wood.