Night Terrors

Night Terrors are living wisps of greenish fog that slip into a person's mouth and haunt them with nightmares while they sleep. Night Terrors live on the fear that these nightmares create. Gradually, their victim becomes weaker, sleeping more and more often each day. Finally, if nothing is done, the victim falls asleep and doesn’t wake up, trapped in their own nightmares until they starve to death.
There are only two ways to fight off a night terror. The first is for the victim to confront their fears and overcome the nightmares. The other option is for another person to take in the night terror (and suffer its effects) by kissing the first victim and willing it to exchange bodies. The terror has no choice but to enter the new body if this occurs.