So, for Chapter 11, the focus might be on the aftermath of the lighthouse incident. They have the map and the device. The map was activated by the lighthouse device, revealing hidden locations. Perhaps they find a new location to investigate based on the map. There could be another ancient structure or a hidden path. Maybe the shadow creature was a guardian of these artifacts, and there are more to confront. Alternatively, there could be a twist where the family learns more about the history of the area—maybe the lighthouse was built over an ancient site, and the artifacts are connected to some prehistoric or magical civilization.