Possible Clues:

• They claim clairvoyance
• They claim to have extra-sensory perception
• Mediums
• Do they really hear if anyone's there or are they hearing things?
• Clairvoyants
• They claim the ability to see the future
• Mind readers
• Hearing sad exhalation thrills mediums
• They claim to have occult powers of communication with the dead
• Mediums for destroying ships - including, initially, yachts, canoes and coracles