We do not have a whole lot of clear teaching in the Bible
about demons and precisely how they operate. It is evident from the various
accounts we have in the gospels that demons are capable of indwelling, tormenting
and periodically controlling humans who become susceptible to them, but we do
not know much more than this for certain.
Under what conditions do demons come and indwell a person? Where do
they go when they haven’t got a human being to play with? Why do they so
terribly fear the abyss, and what makes them crave human hosts while methodically working away at their destruction? None of these things are spelled out for us.