Mysterious ghosts are found during the Curse of the Empty Lord miniquest (although they still appear afterwards). You can only see them when a Ring of visibility is equipped. There are found at various locations throughout Runescape. They can also be spoken to on a F2P world. Each ghost gives a piece of ghostly robes.
There are 6 of them, and though they appear in game as mysterious ghost, they all have names:
• • • • • •