Clockwork Leviathan?

I just had a very strange dream and need to write what I remember of it before it goes away...

During one part of this dream I happened upon an enclosed space much like you would see perhaps at a fancy aquarium, only nicer, it was actually a glass dome surrounded by water and very large. There were sharks swimming around in it... the normal fare.

I found myself pulled to the left hand side of the room, along with another unspecified person I apparently knew. I believe they were my partner or assistant. It was a dark side of the tank, and we were observing the dark rock formations. It just seemed eerie....
My assistant called me over to look at something. It was an eel poking it's head out of the rocks, just... doing what eels do. He seemed friendly, I like eels.
The rocks seem the be churning slightly...There was a human looking face within the rocks. Very creepy. As I wondered what it was, more seemed to appear as the rock formation moved and the room felt heavier and heavier. Suddenly there were eyes... and it became apparent we were never looking at a landscape of rock formations but a massive terrifying creature that surrounded the entirety of the room.

I can not possibly begin to describe this thing, but a sinking feeling of dread and horror rocked me from within my very core. I had never been so frightened in my entire life. I kid you not that I felt real emotion so deep it could never be described and understood in this world... It felt as if something grabbed my soul and squeezed it infusing terror into every string of essence. it makes me tear up just thinking about the emotion.

Did I mention this thing was ginormously huge, and right next to us maybe 4 ft away with only a sheet of glass. It seemed kind of amorphous. Dark and dull but not completely lacking color. It may have had some mechanical parts in addition to the rock looking skin, but mostly it was very slimy and
I wish I could draw it but I would still never get all of the features right because I could barely comprehend what the thing really looked like. The best I can describe is a cross between a few fish, a spider, a slug, a canictis (from King Kong, I know there's a real creature similar to it, but I can't think off the top of my head), and teeth lots of teeth and slimy tentacles.

A voice told me is was a Clockwork Leviathan. And while it was definitely a leviathan by all standards, I can't really figure out to what exactly the Clockwork refers to, as strangely enough it could have meant many things, even though looking at it I'd never have called it that.

I woke up several dreams later, but being so profoundly affected by this creature I naturally decided to do a bit of light research on the net. I can't find anything useful on a Clockwork Leviathan. However I did find something Remarkably close to being the thing in my dream.

It's called Hellmouth...
or The Beast Acheron as depicted in Simon Marmion's miniature painting...

Judging from this info... I can make sense that the figures of humans within the "rock walls" of the beast that we saw were in a similar situation to this... trapped souls trying to escape.
That painting also is strikingly similar to my dream... in a 1400's kind of way.

This has been a truly strange experience.
Anyone have any comments or can dig up any more information on what the beastie in my dream could have been?

Looks like I have a new project on my hands.