(Author's note: This has nothing to do with Illithids, from Dungeons & Dragons. It is instead a combination of the words "ill", meaning bad, and "lith", meaning rock. "Illithic" = "Bad Stone".)
Ever wonder why there are so many haunted castles and so few haunted log cabins? Why caves are scarier than forests? Why "monsters" are more likely to lurk in basements instead of attics?
It's because of all that stone.
No, seriously. Bear with me a moment and I'll prove I'm not on crack.
What would you say if I told you that there was a kind of stone that produced electricity when put under mechanical pressure? You'd call me crazy, right? That's the piezoelectric effect, bitches, and not only is it 100% provable it's also the basis for modern technologies involving transformers, sensors, motors, and clocks. Even zanier, the reverse is also true: apply an electric current to that rock and it will change shape, deforming up to 0.1% of its original dimensions. What's more, it's not just one type of rock that has piezoelectric qualities. There are several of them, and the largest group -- Quartz -- just happens to be the second most common mineral in the Earth's crust.
The human brain produces electricity, and transmits measurable electrical signals at different frequencies. This has also been scientifically proven, and is the basis for the Electroencephalograph, aka the EEG machine.
Those of you who see where this is going may nod knowingly and mock those who don't.
So that brings us to illithics -- bad rocks. Or, to be more technical, crystalline lattices which deform under psychic energy.
Odd, isn't it, how so many historically haunted locales have bloody histories attached to them? Perhaps not. I submit to you that these sites are strewn with -- or in the case of castles, may consist entirely of -- these piezopsychic rocks. They deform under the intense psychic energy that is produced when tragedy and bloodshed occur, distributing the load across their structures. Then, years or centuries later, as mechanical stresses are applied to them -- perhaps through renovation (how many hauntings begin with the new owners starting construction?), or perhaps through the simple repetitive stress of people living there -- the illithics compress, and discharge their stored psychic energy, usually to the detriment of those present.
Castles, of course, are the classic definition, with the entire structure serving as a piezopsychic lattice, but they are not the sole examples. Haunted caves, the monster in the basement under the stairs, old abandoned rock quarries... all have one element in common: they are surrounded by lots and lots of rock.
I admit I cannot prove any of this. But it makes a neat theory. And consider the following: If no one is there to be scared, is a house truly haunted? Or does it require a person to be there, to act as recipient of the psychic energy, for a haunting to take place?
Sure, it may be all in your head. That's where psychic energy originates.