- The universe is very NOT human-centric. Not only are we not at the center of things, the vast majority of everything not of Earth is so alien that just looking at it will screw with your mind.
- Not only is everything else alien, it’s so inimical to earthly life that just hanging around it affects you in different negative ways, from madness to cellular degeneration.
- That all said, there is a sort of universal plasticity to all things, including people. What this means is that while hanging around an alien presence is warping your view of reality and making all your hair fall out, the alien could also actively rewrite your DNA so you sweat the alien’s version of a fine Chianti.
In short, not only is the alien horrific but its effects on you invoke all manner of body horror; the human body is the most alien and horrible thing of all that a human being must endure.
That’s the view from the mountaintops. As you dig into things, certain details have very interesting implications. For instance, Yog-Sothoth is described as “a congeries of iridescent globes, yet stupendous in its malign suggestiveness,” which is a wonderful way to describe a being of four (or more) physical dimensions interacting with your three-dimensional universe. It’s also somehow simultaneously outside our universe and yet coterminous with all of space and time. That means that if you could somehow communicate with/tap into Yog-Sothoth, you could know anything that’s ever happened or ever will happen. Likewise, you could travel to anywhere or anywhen. Imagine that as a method for FTL travel. You can get to Alpha Centari in mere minutes, but you have to travel through Yog-Sothoth to do it. Makes 40k’s Immaterium look like River City, Iowa.
Azathoth “blasphemes and bubbles at the center of all infinity” and “gnaws hungrily in inconceivable, unlighted chambers beyond time and space amidst the muffled, maddening beating of vile drums and the thin monotonous whine of accursed flutes.” Witches pledge themselves to it for their strange powers. Nyarlathotep is a go-between for humans and Azathoth, and can somehow bridge the divide between the human and the alien.
The Earth is infested with ancient alien beings like Cthulhu, trapped in a death-like sleep until “the stars are right.” It influences the dreams of humanity, inspiring worshipful cults, though just what the cults or Cthulhu get out of it, if anything, is never explained. By comparison, Dagon is much more straight-forward, trading rich fishing and bizarre gold jewelry for breeding-rights.
Luckily, you can escape all this body-horror and whatnot by transporting your consciousness to another body. Unfortunately, that body is likely to be even more utterly alien, like the Great Race of Yith that enjoys swapping consciousness with modern humans and going joy-riding in their bodies. These things clearly are on good terms with Yog-Sothoth since distances of time and space don’t deter their non-consensual consciousness-swapping ways.
And if swapping bodies isn’t your thing, you can always send your consciousness into the Dreamlands, a realm where powerful beings live double existences, where the “gods of earth” might dwell (when they’re not slumming it in Boston) and where the ghouls apparently go when they’re not eating people in the sewers.
And that might explain how you can hop into another body, with its own individual brain and chemistry, and yet retain your memories and personality; your “true mind” (or, at least, a reasonable facsimile thereof) exists in the Dreamlands and not in the flesh and chemicals of the brain and the limbic system. Those are just interface tools.