Skull

 is a body part that can be extracted from a corpse at the autopsy table. Upon removal, it has the effect of adding one Red Skull. In addition, similar to most other anatomy and theology items, it can be studied at the Study table for a reward. For more information, see corpses. They're also utilized in the buildings of various constructs when using the Dark design desk.

Bring me a skull
After talking at length with Gerry, he will eventually inform you of the Astrologer. Upon meeting him, he will ask you to retrieve a from a corpse. Returning with one will kick off the Astrologer's quest-line, and open up the potential for trade.