Seeing a ghost

The most distressing during sleep paralysis is seeing an intruder that sometimes attacks the sleeper. Anything the imagination can invent can happen. Commonly, the intruder chokes the person by crushing his chest. The creature can include details like a demonic face with sharp teeth and cat eyes.

One explanation is that in the same way that people who are born with a missing arm may experience phantom limbs - they feel the missing limb - a person can 'feel' another phantom person during sleep paralysis.