Ghost
From YPPedia

Islands with ghosts appear dark.
Ghosts help pirates find out where zombies and skellies are.
Finding Ghosts
Ghosts sense the unbalance of the ocean and will likely tell pirates where there may be a infestation of skellies or zombies. Unlike skellies and zombies, ghosts walk around, so pirates may have to search for them.
Commune with the Dead
There is only one option on a ghost's radial menu, which is Commune with the Dead. When this option is clicked on, the ghost will send a tell as to where there may be skellies or zombies.
For skeletons, the message will be one of the following:
- "I sense a horde of Skeletons on <Island>."
- "I sense a legion of Skeletons on <Island>."
- "There be Skeletons besieging <Island>."
- "There be Restless Bones besieging <Island>."
- "Skeletons have overrun <Island>."