Somewhere at the bottom of the ocean floor, far below the point where darkness would blind and pressure would kill, lies an abomination. It has been there for thousands of years, and will continue to be there for thousands to come. Its physical structure is not in the realm of what science knows as possible, and this is because it is a guardian of Hell.
Well, "Hell" anyway. A place thousands of light years away in a place where things exist half-in and half-out of matter, where dark energy clashes chaotically in unimaginable quantities. Tales of it exist in texts from long ago, but in their small minds and through their dark ages the new humans understood it to be the only place where this happens, much like the belief of only one "Heaven." In truth its only one of such places.
The abomination used to live there, long, long ago. To keep a story short, lets just say he got into a scuffle with the family and ended up sleeping on wet dirt at the bottom of a sea in some small-time shit planet at the edge of a small galaxy in the middle of nowhere in particular. Our loved and lovely earth.
It has no equal on said earth, so it lives without fear. It knows that no one can fuck with it, and not for lack of trying. Sorcerers and Conjurers of spells from many human ages have tried to approach it, to dominate it, to manipulate it. If there was a hell they would wish for it now, their fate far worse than any eternity in such a place.
But at the moment existence doesn't need it, has no use for it, so it lies almost soundlessly in the deep. Almost. Sometimes you can hear it: