Monsters and ghosts? Your own mind and desires. It can be heard here:
The struggle between spiritual/religious beliefs and sexuality is real. Ever fought off your own desires to the point where it drove you insane? It doesn’t have to be sexual desires you fought off, but sexual desire is a strong force. Fighting it will make you scream to the heavens and recite spiritual/religious chants… And giving in is like giving in to Satan himself/herself…

As Keanu Reeves character on Constantine once said “Angels and Demons can’t cross over into our plane. So, instead we get what I call half-breeds. The influence peddlers. They can only whisper in our ears. A single word can give you courage, or turn your favorite pleasure into your worst nightmare.”
Without our own personal internal laws, rites, as well as spiritual connections, we are impulsive beings. Impulse purchasing, impulse killing, etc. Without those laws, most of us will turn into devil’s… People will eat people. Meditate on that.