If you haven't already, watch the first few seasons of the program "Supernatural" on the CW network.
I've learned a quite a bit about the spectrum of possibilities we could be dealing with thanks to watching that show.
The way it portrays demon possession, the black eyes, the demon smoke taking possession, etc., explains the unexplainable in our "real" world fairly well.
That reminds me...I need to stock up on Holy Water I keep by the front door for the political door knockers this election season.
The Jehovah Witnesses and all the "Hail damaged roof?" sales people have emptied my supply. They are legion.
I actually answered the JW knock once stark naked. On purpose. No joke.
They never came back. Mission accomplished.
I don’t actually blame them...Probably made them question a lot of things, including their faith ;)