Other forms: phantoms
Look over there, across the room. Is that a phantom, some weary soul come back from the dead to haunt you? Maybe it’s a shadow, or maybe it’s a ghost. Either way, turn on a light and it’ll disappear. Hopefully.
Sleeping is difficult if there’s a phantom in your room, because who can rest with ghosts around? Some phantoms are real, but phantom can also be used to mean "a trick of the mind," like hearing a person outside your window, but then realizing it’s only the phantom rustling of leaves in a tree. Phantom limb is when someone loses an arm or leg, but their brain can still feel where their limb used to be.