I know what the Greys
The Greys are fear. Simple animal terror with a face hung on it. Strange men, inscrutable and mysterious, implacible and hostile. We want to explain them to ourselves, to make them a known quantity, so we tell ourselves these stories about how they come from outer space to perform medical experiments. Lies. They've always been here.
Mankind has always been afraid of the thing in the dark, the thing we don't understand. To a tribesman who has never gotten a good look at the tiger, it is the night come alive to kill and devour his friends. To a Victorian explorer, it's just a dumb animal, helpless once you take a few precautions. But then, the Victorians had Dracula to worry about.
Vampires. They come at night, to take away the innocent and do with them as they will. They drain blood for their evil schemes. They can change into a bat, or a mist, making them invisible, intangible, unstoppable.
They were here.
Horseshoes were hung over doorways because the 'little people' hated cold iron. If you weren't careful, the fey folk would spirit you away. Call them nice names, like the Fair Folk, or the Lords and Ladies, or they'll come and pinch you in the night. Changeling children were left in the place of babies taken in the dark.
Taken in the night. They were here.
Mythology is full of this same repeating theme. The mysterious thing that comes in the night to take the unwary. Look close, and you realise that all the details and facts about the monster are just storytelling. Garlic? Cold iron? Tinfoil hats? We construct these elaborate fictions about the nature of a monster so we can sleep at night, but it's all lies. We don't know what it is, and that terrifies us.
The meta-monster is only an alien now because we read science fiction, and the last great unknown is Space. Man feels terror, and he instictively knows the only way to beat it is to know his enemy. But this enemy has remained unknown for all of history, and man simply guesses at what it can be. The story gets passed on, and embellished, and explained, until it's a myth.
But the myth started somewhere. They were here.
What are they? My cold, rational mind tells me that the Greys, or whatever the meta-monster is in the local culture, is a psycological creation to explain what amounts to fear of the dark. The powers traditionally assigned to the meta-monster tend toward the violation of man and his security - flying over walls, walking through locked doors, paralysing victims, vanishing into the night. It's always a creature that can't be stopped or resisted in any normal way. This is the personification of fear.
Late at night, however, when my rational mind has clocked out for the night, I have to wonder if we're using our fear against ourselves, or something is using our fear against us. Has been using our fear for as long as written history goes back.
Whatever they are, they were just outside the campfire light two millenia ago, and they will be there tonight when you turn off the light and sleep. You can't lock the door on your fears, boys and girls - they will find a way in to where you lie sleeping and helpless tonight.
They always have.