Looking back on the film universe that Marvel has created, it's hard not to be impressed. It has been ten years and grown to a whopping twenty movies since Iron Man was released. But there is still so much more to come.

It's a success story unlike most, as Marvel Comics had to sell film rights to other companies to stay afloat, meaning they couldn't bring in some of their more popular characters like Spider-Man and the X-Men. But those times have long passed and the Marvel Cinematic Universe is the biggest film franchise around.

One of the most impressive qualities about the MCU is how it was built on the foundation of heroes that the general public may not have known. Everyone loves Spider-Man and the X-Men, but heroes like Iron Man and Captain America couldn't hold a candle to them in terms of popularity. But now, it's hard to imagine the MCU without them. That's exactly where we're heading though.

While some characters may continue on, the MCU proves to be making room for others to join in on the fun. Marvel has generally stuck to realism on Earth, but mega-producer Kevin Feige has stated they want to start moving to more cosmic and otherworldly characters in the future, as well as featuring more diverse characters. Some of them have been mentioned by name, but Feige and Disney seem to want to keep others a secret.

As their film world expands, Marvel will be able to tell new stories with a unique variety of characters. Here are 15 characters they are sure to include in some way, and 15 they won't.

30 Will appear - Nova

Via: webdnet.com

When Marvel started looking at more cosmic characters to include in the future, the one that was brought to the minds of most fans was Nova.

The Nova Corps were already seen in Guardians of the Galaxy, so it would be incredibly easy for Marvel to bring the character in.

But Nova is also one of the characters Kevin Feige has stated is most likely coming, so it seems like we won’t have to wait long before we see him. Whether it would be the original Richard Rider or Sam Alexander is unclear, but either would be a welcome addition.

29 Won't Appear - Iron Man

Via: wegotthiscovered.com

By now, it is common knowledge that Robert Downey Jr.’s contract with Marvel will be expiring soon. And while it will be sad to see him go, he has taken the character as far as he can go.

He began the saga that would grow to be the Marvel Cinematic Universe and his send-off will most likely be a heartfelt one. But his departure will make room for Marvel to bring in a ton of new characters. And perhaps, one day, this exit will lead to an Ironheart movie.

28 Will Appear - Adam Warlock

Via. superherostuff.com

Here we have another cosmic shoo-in, as the character was name dropped during one of the many credits scenes in Guardians of the Galaxy Vol. 2. It’s unclear if he’ll make his debut in Guardians of the Galaxy Vol. 3 or someplace else, but his inclusion is something fans have been clamoring for.

While he comes with the standard superhero powers of increased strength, speed, and durability, he can shoot energy beams from his hands and create a cocoon for himself to regenerate in as well. He is also, essentially, immortal.

27 Won't Appear - Mandarin

Via: marvel.wikia.com

The Mandarin twist from Iron Man 3 understandably left a lot of fans upset since the character is one of Tony Stark's greatest foes. It's incredibly unlikely that the character would appear in Phase 4, let alone in the universe at all, for a couple of reasons.

While the real Mandarin was confirmed to exist in the short All Hail The King, it doesn’t seem like Marvel would revisit him due to the bad taste that twist left in everyone’s mouths. But also, Robert Downey Jr.’s contract will be up soon, and the villain is linked to Iron Man.

26 Will Appear - Mysterio

Via: geektyrant.com

The film that will kick off Marvel's fourth phase is Spider-Man: Far From Home. And the central villain that the wall crawler will be going up against has already been confirmed to be the Master of Illusions.

Don’t let his silly costume fool you; Mysterio is not to be trifled with.

He doesn’t have any powers, but he’s never needed them. He is an expert in illusions, special effects, hypnotism, stage magic, misdirection, and several forms of hand-to-hand combat. So it seems like Spidey will have his hands full.

25 Won't Appear - Green Goblin

Via: artstation.com (Woochun Choi)

Though he may be Peter Park’s arch nemesis, don’t expect to see Green Goblin in the MCU anytime soon. Marvel seems more interested in bringing the villains we haven’t seen before to the big screen, such as Vulture and Mysterio.

We’ve already been given two live-action versions of the Green Goblin, once in Sam Raimi’s Spider-Man and once in Marc Webb's The Amazing Spider-Man 2. It’s possible they would include the villain eventually, but not nearly as early as Phase 4. Saving him for later would be the smarter move.

24 Will Appear - The Eternals

Via: geektyrant.com

The Eternals are one of the oldest races from Marvel Comics, and one that Kevin Feige has also expressed interest in bringing to the big screen.

Though relatively unknown to the general public, it would make a lot of sense to bring them in soon.

They are a race of super-powered beings and the product of experimentation on early humans by the Celestials, first seen in the Guardians of the Galaxy films. Their inclusion will offer some answers about the greater universe and scratch the cosmic itch that many Marvel fans have.

23 Won't Appear - X-Men

Via: cbr.com

While it would be possible for the MCU to see a mutant or two appear, the Fox/Disney merger may be too recent to see them in Phase 4.

Marvel was able to get Spider-Man into the MCU quickly after getting the film rights back, but that was just one character.

And right now, Marvel seem to have their hands full with transitioning some heroes out and bringing others in. Writing in the existence of mutants and bringing in a team of that size would make for an even more cramped universe.

22 Will Appear - Mephisto

Via: comicbook.com

Mephisto is one of many Devil-esque characters in Marvel Comics, but he would be the easiest one to bring into the MCU by far. For one, he would be an excellent supernatural villain and would therefore fit well with the direction Marvel seems to be moving.

But also, he is the creator of the Spirit of Vengeance known as Ghost Rider, who has already been seen in the MCU on Agents of S.H.I.E.L.D. He has also crossed paths with a large number of heroes in the comics, so his inclusion seems like a no-brainer.

21 Won't Appear - Steve Rogers

Via: syfy.com

As is the case with Robert Downey, Jr. as Iron Man, Chris Evans will soon be leaving the MCU. It may be through retirement, making way for another hero to pick up the mantle like Sam Wilson or Bucky Barnes have in the comics. Or it may be something much sadder.

Cap is one of the few heroes who provides the backbone for the entire MCU, and the epic owes just as much to him as it does to Iron Man. But also, like Iron Man, his departure will provide room for new characters to exist.

20 Will Appear - Namor

Via: cbr.com

While it could be argued that Marvel wouldn’t introduce their version of the King of Atlantis while DC is currently showing off theirs, there’s no denying how important Namor’s inclusion would be.

He was already hinted at way back in Iron Man 2 along with Black Panther, who was eventually brought into the MCU.

Speaking of Black Panther, Namor has been a villain to T’Challa in the comics. And since he has already faced his two most well-known foes, it seems like bringing in the Sub-Mariner would be the next natural step. The groundwork has already been laid out.

19 Won't Appear - The Fantastic Four

Via: syfy.com

The case of the Fantastic Four is similar to that of the X-Men. The deal between Disney and Fox will be too recent to see them show up in Phase 4.

But there’s also the fact that of the three film adaptations the team has received, none of them were well-received. Marvel may want to give it some time before bringing them in. They’ll fit in well with the cosmic direction Marvel wants to go in, but it’s more likely that events in Phase 4 will lead to the creation of the team in Phase 5.

18 Will Appear - Quasar

Via: movieamigos.com

But here’s a cosmic hero that would be incredibly easy for Marvel to introduce. The mantle of Quasar has been held by several characters in the comics, so Marvel has a number of people to choose from. But most of them received their powers by wearing alien technology called the Quantum Bands that allow them to create force fields and shoot energy beams.

Plus, different versions of the hero have teamed up with other cosmic heroes like the Guardians of the Galaxy and Captain Marvel. If Marvel wants more characters in outer space, Quasar is a safe bet.

17 Won't Appear - Moon Knight

Via: screenrant.com

Of the characters on the “won’t” list, fan demand for Moon Knight’s live-action debut may be the highest. While not exactly a household name, he has a huge cult following.

But getting the character right on film would be tricky as Marc Spector has multiple personalities. His series may also be a bit dark for Disney. He would’ve fit in well with the tone of the Netflix shows, but it’s unlikely we’ll get more heroes there due to Disney’s own streaming service plans. Kevin Feige has acknowledged the character’s popularity, so hopefully we’ll see him pop up down the road.

16 Will Appear - Nightmare

Via: powerlisting.wikia.com

Doctor Strange 2 is one of the sequels we’ll obviously be getting very soon. The character has been well-liked in his own movie as well as Avengers: Infinity War, and he’s one of the only heroes in the MCU currently that deals with the supernatural.

It’s likely Baron Mordo will show up again since the character only turned to villainy at the end of Doctor Strange. But it is also likely we’ll get Nightmare, who is one of Strange’s greatest foes from the comics. The ruler of the Dream Dimension would make an excellent main villain for Strange to face.

15 Won't Appear - Hercules

Via: inverse.com

The MCU has primarily focused on Norse mythology, but there are a ton of characters from different mythologies in the comics.

One such is the demigod Hercules from Greek Mythology.

His boisterous personality would fit in extremely well with some of the heroes we already have, but it’s unlikely Marvel would choose to include him just yet due to the fact that they are still exploring Thor and his kind. Maybe once the MCU expands mythically, we’ll get a Hercules movie. Seeing him face off against Ares or Achelous would make for an incredible fight.

14 Will Appear - Valkyrie

Via: polygon.com

Of the awesome things to be included in Thor: Ragnarok, of which there were many, Tessa Thompson’s portrayal of Valkyrie was a definite highlight.

But in Avengers: Infinity War, the character was nowhere to be seen, leaving many fans wondering about her status.

That question will likely be answered in Avengers 4, but there’s no way that will be the character’s last appearance. She became instantly popular after Ragnarok’s release, so the MCU will probably feature her in another movie during Phase 4. She also helps the diversity of the MCU, as the character is bi.

13 Won't Appear - Amadeus Cho

Via: YouTube.com (La Historia De - Solo Comics)

There’s a lot of fan demand to see some legacy heroes like Kamala Khan and Miles Morales make an appearance in the MCU. But there doesn’t seem to be any around Amadeus Cho aka the Totally Awesome Hulk.

He’s a great character, but the MCU already has one Hulk.

And even if Bruce Banner were to exit the MCU, it is more likely we would get a different Hulk character. Fans have been craving the introduction of Jennifer Walters aka She-Hulk for years, and we’ve already seen Thaddeus Ross, who becomes the Red Hulk in the comics.

12 Will Appear - Scorpion

Via: playstation.com

While Mysterio will definitely be the main antagonist of Spider-Man: Far From Home, he certainly won’t be the only one.

One of Spidey’s classic villains, Scorpion, was teased with a cameo in Spider-Man: Homecoming. Played by actor Michael Mando, the character appeared as an associate of the Vulture and his identity was given away by a neck tattoo of (duh) a scorpion. Though he wasn’t the super villain yet, the first film of Phase 4 will probably see him turn into a greater threat to Peter Parker.

11 Won't Appear - Venom

Via: gamesradar.com

No matter how bad fans may want it, it doesn’t seem like the upcoming Venom film will be connected to the MCU. This is a real shame, because seeing Spider-Man face off against one of his most popular enemies would probably equate to cinematic gold.

Sony has had a couple of chances now with the universe of Spider-Man, and if this were to fail too, Marvel could maybe acquire the film rights to bring Eddie Brock in. But even if that were to happen, it would too soon to include the character in as early as Phase 4.