The first Marvel Studios' special presentation, Werewolf by Night, has opened up the monstrous side of the Marvel Cinematic Universe to the rest of the MCU. Both critics and fans have been very positive towards the project, as evident by the 91% score it has on Rotten Tomatoes. It's safe to say that individuals like Jack (Werewolf by Night) and Ted (Man-Thing) will make their presence known around the MCU.
With the creative swings that Marvel Studios have taken in Phase 4 of the MCU, especially in Werewolf by Night. It shows that this growing universe has plenty of room for unique characters like an aquatic powerhouse, a self-aware zombie, or even a space Kaiju.
Behemoth
The concept of Behemoth is similar to Ultron's origin in the MCU: both were created to protect their communities from future threats. The Behemoth is an aquatic beast that came from the mind of Atlantean scientists and was buried underneath the city of Atlantis as it was too powerful for the Atlanteans to contain. The character's first appearance was in Tales to Astonish #77, created by the team of Stan Lee, Adam Austin, and Bill Everett.
Behemoth is a powerful creature of the ocean that has superhuman strength, durability, and resistance to injury. A potential appearance would likely involve Namor the Sub-Mariner in some manner, as the two have crossed paths before. Tenoch Huerta will portray Namor in his live-action debut in Black Panther: Wakanda Forever. With that debut, the door would be open for Behemoth to make an appearance as an ally or a foe to Namor.
Manphibian
Manphibian, an amphibious alien creature, is a fierce protector of the monsters of earth against the forces that want to use and abuse them. The character first appeared alongside Frankenstein's Monster and Count Dracula in Legion of Monsters #1. The character was created by the team of Marv Wolfman, Tony Isabella, Dave Cockrum, and Sam Grainger.
The character resembles the "Gill Man" of the Creature from the Black Lagoon franchise. Manphibian possesses razor-sharp claws, superhuman strength, and skin that is strong enough to withstand missile strikes. Any future appearance by either Jack Russell or Elsa Bloodstone in the MCU would be a good place to see Manphibian make his live-action debut. Both Russell and Bloodstone have been considered some of Manphibian's greatest allies throughout the character's history.
Simon Garth, The Zombie
Simon Garth was a New Orleans-based businessman known to be a harsh boss to his employees. His former gardener (whom he fired) kidnaps and offers Garth to a voodoo cult as a human sacrifice. The gardener forced a member of the cult, Layla (who happened to be Garth's secretary), to transform him. Layla calls upon the serpent god, Damballah, to resurrect him as a mindless Zombie. Amulets were placed on Garth and the gardener who had brought him there first to link the pair.
Garth has super strength and a healing factor that would make him a worthy opponent for most characters in the MCU. He wears the Amulet of Damballah around his neck; he must obey the wishes of anyone who holds the duplicate of the Amulet.
Monster From Mars
The Monster from Mars is one of the first foes that squared off against Marvel's first family. Appearing in Fantastic Four #3 in December 1961, the Monster from Mars was a creature display from a film of the same name that was brought to life by Miracle Man, another lesser-known character from The Fantastic Four rogues gallery.
With Marvel Studios' continuing its tradition of reinventing lesser-known characters for live-action and the MCU version of The Fantastic Four coming in 2025. It seems like this vintage space Kaiju would be an interesting villain for The Fantastic Four.
Dracula
The Lord of the Vampires, Dracula, has been one of the most popular choices to be the main antagonist of the MCU's Blade movie. Much like the opening scene of Werewolf by Night was explained, monsters like vampires have been hiding in the shadows for centuries.
Dracula is an immortal being with superhuman abilities, sorcery, and mind control. He is also brilliant and has a healing factor that is quite useful against any opponent. Like other depictions of vampires across media, he becomes more at risk of losing his immortality if he does not consume enough blood.
N'Kantu, The Living Mummy
N'kantu was born a Warrior-King but was forced into slavery. He led a movement to overthrow Aram-set, an evil pharaoh who had been abducting and enslaving his people. His efforts failed, and, as punishment, he was mummified and trapped in a tomb for generations, leaving him undead and unable to move or speak.
Eventually, he is freed and begins a new life as the Living Mummy, becoming an adventurer and wanderer who struggles to connect with people because of his appearance. N'kantu carries out the wishes of the Egyptian god Anubis like how Moon Knight carried out the wishes of Khonshu in the MCU.
Tricephalous
Tricephalous is similar in appearance to King Ghidorah from the Godzilla franchise. Both are menacing, fantastical, and the epitome of what a monster would look like to most people. The character was introduced as a servant of the Mole Man in one of the first Fantastic Four comics.
Tricephalous' abilities include super strength, flight, and fire breath from each of its three heads. It's the kind of character that could be a great challenge for a crossover team of new Avengers introduced in Phase 4.
Xemnu
This character was the original Hulk, making his debut two years before the Bruce Banner version of the Hulk did in 1962. Once he was introduced, Xemnu the Hulk was renamed Xemnu the Titan to avoid confusion between the two characters.
He was an escaped alien criminal that landed on earth to repopulate his race through evil schemes. He has been an enemy of the Hulk for years; his mentality is to dominate any creature he encounters.
Devil Dinosaur
The whole theme of the MCU's current saga involves the consequences of tampering with the multiverse. Imagine seeing Dr. Strange and America Chavez spending more time in that universe with dinosaurs in the background. What if the duo wandered around and accidentally into an apex predator's territory, a red mutated Tyrannosaurus Rex named Devil Dinosaur?
Devil Dinosaur has super strength and is highly resilient to most attacks. Throughout the character's history, Devil Dinosaur has been paired up with a few characters that have brought out different sides of the character.
Franken-Castle
Frank Castle, The Punisher, is notorious for being one of the more grounded and dangerous characters in the Marvel universe. But imagine he was brought back from the dead to fight evil. Crazy right? Well, it actually happened.
With the absurdity of a character like this, it seems like a live-action appearance would be a bit hard to achieve, even by MCU standards. But it might be perfect for an animated appearance in either What If...? or Marvel Zombies.