Warning! Spoilers ahead for Darkhold: Spider-Man #1
In a very disturbing one-shot issue from Marvel Comics, Darkhold: Spider-Man #1 reveals the horrifying truth behind the body of Reed Richards of the Fantastic Four. After reading from the Darkhold, Peter Parker's Spider-Man is shown a dark alternate reality where the entire world has begun to unravel. In an effort to hold his city and its people together, this reality's Spider-Man spends every day webbing up as many as he can to keep them from dying and falling to pieces. However, Peter himself is fine thanks to his accelerated healing along with Reed Richards whose powers of elasticity have kept him together as well. However, the absence of actual human life beyond Spider-Man has revealed Reed's true natural state (which is truly quite horrifying).
In Darkhold: Spider-Man #1 from writer Alex Paknadel and artist Dio Neves, Spider-Man has hardly slept or eaten, constantly needing to web and re-web the city to keep as much as he can in one piece as possible. Effectively, Spider-Man is living in a city of people who have the fragility and mental capacity of zombies, capable of losing body parts and whole limbs at random if Peter isn't there to help keep everything attached, always needing to reapply as his webs dissolve every few hours. However, Reed Richards has been trying to help Spider-Man find a more permanent solution to the problem.
Horrifyingly, when Spider-Man visits the Baxter Building (where Reed is seemingly the last surviving member of the Fantastic Four), Spider-Man discovers Mr. Fantastic as nothing more than a misshapen and grotesque puddle of flesh. While Reed quickly reassures Peter that he's alright, he's truly awful to look at. Furthermore, Reed confirms that being said puddle frees up his mind to continue his work while also suggesting that without humanity as it once was, this unaltered liquid state is actually his true form.
Reed goes on to explain that his "mirror neurons were aping observed human anatomy as well as behavior" which essentially means that his puddle form is what he truly looks like without his neurons mimicking the living humans around him. While it's unclear if the worlds seen in these Darkhold one-shots are true alternate universes in the multiverse or dark fictions created by the Darkhold's creator Chthon, it stands to reason that this fact about Reed's powers could also be the case in the standard 616 universe (which holds the primary Marvel continuity).
Without humanity, a grotesque sloshing puddle seems to be Reed Richards' true state in the Marvel Universe. Thanks to this new one-shot, it's been revealed that Mr. Fantastic only looks like a human simply because being around other humans makes his body thinks he is human too and helps him maintain the appearance of the man he was before being exposed to cosmic rays along with the rest of the Fantastic Four. While interesting and horrifying at the same time, it doesn't change the fact that this desperate Spider-Man turned Reed Richards himself into a dark and longer-lasting web fluid by the one-shot's end, forcing Mr. Fantastic to keep the world together despite the agony.