Common concept of a creature living in another creature, absorbing their nutrients and abilities without given anything in return.
I don't need to elaborate I think.
Interesting how interesting some parasytes first appear to be. Many a colorful fungus or worm has a curious shape. Its almost as if a brightly colored or interesting looking exterior facilitates the infestation.
So the parasyte mimics the behavior of the host, and discerns what the hosts find "interesting". Thus the host picks up the parasyte, and gives nurtients of its own free will.
I wonder how the parasyte feels, needing others to survive?
The worst sort of potential a person can have is wasted potential.
Sloth is a potent sin indeed.