An unreleased set shown on the 4th version of the map. Its a Skeleton Crew owned place. It is not a prototype for the Privateers Lighthouse because it was shown at the toy fair with it. I believe that this set was a prototype of the Sketeton Crew Prison. I think the ghost looking guys are early lost souls.
It was the main Prison of the Skeletons, where prisoners were taken before their fate was chosen. The Skeletons would consider whether they would be enslaved on board the Phantom, or Pyrate's Cove.