Wait... Hellish red eyed cavern entrance, small river before it (though not exactly big enough for a boat - still, could represent Styx), as already pointed out, red eyed demon looking out from the dark, from the background though not obvious, it seems like this is just a small hill, which could mean that the cave leads underground as opposed to into a mountain...
I know Styx comes later and the entrance should be a tree stump, but... I can't shake the feeling that this is the Equestrian version of the CMC re-enacting Dante's Divine Comedy.
If so, (or even if not) could you make a picture with Purgatory and Heaven as well?
And on a note, completely out of the blue: Think "South Park" and "Little foal you're going to hell." You're welcome.