This is a hallucination. A manifestation of fear from self. Your boyfriend most likely is experiencing his own self hatred superimposed over a familiar fear. Perhaps aliens and demons. This is rather common in schizophrenia but sometime can be induced by stress. Mental hospital.
Your boyfriend needs to get off the meth or pot or or whatever he's taking. Or stop drinking and watching scary movies! The beings we refer to ss 'demons' are spirit beings. Technically they are 'angels' cast from heaven. They only have silly physical forms in movies and TV.