It's been ten years since the Marvel Cinematic Universe kicked off with Iron Man. Beating all expectations, the saga won over audiences all around the world and over time, it became one of the most profitable franchises of all time. Eventually, the MCU's astounding success allowed its mythology to expand outside of the big screen, and tackle mediums like television and even comic books. The franchise's expansion proved to be a smart move, but it hasn't come without its fair share of challenges. After ten years worth of storylines spread across multiple platforms, for example, maintaining a cohesive cinematic universe can become a difficult endeavor.

To prevent things from getting too complicated, the MCU constantly uses its film, TV and comic book corners as a unified support structure for its ever-expanding mythology. As a result, the big screen side of the MCU has often found itself relying on comics and TV series to expand on important aspects of its storylines and characters. So far, that approach has worked wonders for the MCU, and has helped the franchise feel like a true interconnected world. With that in mind, let's take a look at 15 important things from the MCU that were revealed outside the movies:

15 WHY TONY STARK APPROACHED GENERAL ROSS

The Incredible Hulk sent fans into a frenzy with its closing scene, which showed Tony Stark approaching General Ross to discuss the Avengers Initiative. At the time, the sequence seemed to set up an interesting story thread for The Avengers. As the MCU progressed, however, the scene faded into obscurity, and fans were left wondering why Stark had met with Ross. Fortunately, Marvel cleared up the mystery with The Consultant One-Shot.

In the short, Agents Coulson and Sitwell discussed the fact that the World Security Council wanted General Ross to hand over Abomination to turn him into an Avenger. Desperate to dissuade Ross from playing along, the agents decided to send a consultant to annoy the general and discourage him from releasing Blonsky. The consultant ended up being Tony Stark, and thus, the billionaire's role in The Incredible Hulk became an elaborate strategy from S.H.I.E.L.D.

14 JUSTIN HAMMER IS BACK IN ACTION AFTER IRON MAN 2

Justin Hammer in the MCU

Iron Man 2 introduced audiences to Justin Hammer, a ruthless businessman hellbent on destroying Tony Stark. The character resonated with audiences thanks, in large part, to his quirky personality, and he quickly became one of the MCU's favorite baddies. To fans' dismay, Hammer essentially disappeared from the MCU after Iron Man 2, and comic book faithfuls were left wondering what had become of him.

The mystery surrounding Hammer was answered in Netflix's Luke Cage. During the show's first season, it was revealed that Hammer Industries weapons were being sold to criminals around Harlem, implying that Justin had gone back to his villainous efforts. While Hammer himself never actually appeared in the show, it was a nice surprise to know he was still out there. Who knows? Perhaps we'll see him stirring trouble for Tony Stark again at some point in the future.

13 PEGGY CARTER'S SPY CAREER

Peggy Carter made her Marvel Cinematic Universe debut in Captain America: The First Avenger. The character turned out to be one of the best parts of the film, and she instantly became a fan-favorite. Sadly, following her stellar debut, Peggy took a backseat to the ever-growing MCU, and fans were left craving to see more of the character's adventures as a government agent. Fortunately, the character returned to the spotlight in 2013 with the One-Shot Agent Carter.

The short film (which followed Peggy in a not-so-undercover mission) became a big hit, and it encouraged Marvel Entertainment to greenlight a show centered around Peggy Carter. The show only lasted two seasons, but it served as a great insight into Peggy's adventures post-The First Avenger, and cemented her as one of the strongest characters in the MCU. Here's hoping her story will find a way to continue.

12 HOW THE AVENGERS LEARNED ABOUT LOKI'S SCEPTER

Age of Ultron opened with the Avengers fighting their way into a Sokovian Hydra base. Aside from cleaning up Hydra, the heroes travelled there to retrieve Loki's scepter, which they had been looking for since the end of the first Avengers. The film never explained how exactly Earth's Mightiest Heroes came across the weapon's location after such a long search, but dedicated fans got an explanation in Agents of S.H.I.E.L.D.

During the season two episode "The Dirty Half Dozen," Coulson and his team raided a Hydra base to free prisoners being held by the evil organization. Unbeknownst to the rest of his squad, Coulson's main objective wasn't to rescue people, but to obtain an important piece of information from Hydra's database: the location of Loki's scepter. After extracting the data, Coulson contacted Maria Hill and sent her the intel so she could, in turn, forward it to the Avengers.

11 KAECILIUS' BACKSTORY

For his first solo feature, Stephen Strange was pitted against Kaecilius, a powerful sorcerer looking to bring the end to the world. Kaecilius proved to be a worthy adversary for the Sorcerer Supreme, but the film didn't provide much in terms of backstory for the character. Instead, Marvel explored the baddie's origin story in the Doctor Strange prelude comic book. According to the book, Kaecilius sought out Kamar-Taj to find a new purpose in life after the death of his family.

The Ancient One took him in, and after years of training, he became one of her most trusted students. Eventually, Kaecilius was inducted into an elite group of mystical masters tasked with protecting the Earth from other-worldly threats. Such a stellar career made his fall from grace all the more painful, and in a way, the prelude comic turned Kaecilius into one of the MCU's most compelling baddies.

10 HOW NICK FURY GOT A HELICARRIER IN AGE OF ULTRON

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Helping the Avengers find Loki's scepter wasn't the only tie-in Agents of S.H.I.E.L.D. had with Age of Ultron. During the film's third act, Ultron raised the country of Sokovia off the ground, intending to use it as a meteorite. The Avengers' only option was to destroy the chunk of land, but they had no way of evacuating all the civilians on it. Fortunately, Nick Fury showed up at the last minute piloting a new helicarrier, and helped get everyone to safety.

The movie didn't delve into how Fury got his hands on a helicarrier after S.H.I.E.L.D.'s collapse, but fans were given an explanation in Agents of S.H.I.E.L.D. As it turned out, the helicarrier was fixed by Coulson as part of the Theta Protocol, a protocol focused on repairing old helicarriers in case of emergencies. Hence, once Ultron's Sokovia attack began, Fury had a ship ready to offer a helping hand.

9 ABOMINATION'S FATE

Abomination from The Incredible Hulk

Bruce Banner has fought numerous adversaries in the MCU, but few have been as dangerous as Emil Blonsky, aka the Abomination, the main baddie in 2008's The Incredible Hulk. Near the end of the film, following a brutal encounter, Hulk beat Abomination and left him to the authorities. The villain's fate after that remained a mystery for years, until the Marvel One-Shot, The Consultant, where it was revealed that Blonsky was in government custody.

Years after that, Marvel offered a more in-depth explanation on the villain's whereabouts through Agents of S.H.I.E.L.D. During the season one episode "T.R.A.C.K.S.," Coulson learned about Grant Ward and Melinda May's relationship. Furious, Coulson threatened Ward with assigning him to Emil Blonsky's cryo-cell in Alaska, thus revealing the baddie was still in custody. The Abomination hasn't been referenced since that episode, but it's nice to have an idea of what happened to him.

8 SIF'S TRUE LOVE

Lady Sif Shield

Ever since her debut in Thor, Sif has been one of the MCU's most well-liked characters. However, given her small roles in the franchise, the hero has also remained largely a mystery. Fortunately, Agents of S.H.I.E.L.D., gave fans an interesting glimpse into Sif's backstory, specifically, her love life. During the episode "Yes Men," an Asgardian sorceress called Lorelei with the power to control men came to Earth.

Sif was sent after her, and the two eventually met and fought. During their battle, Lorelei revealed that centuries prior, Sif had a partner named Haldor, whom she was madly in love with. Sadly, Lorelei mind-controlled him and forced him to do her bidding. Sif silenced Lorelei before she could continue speaking, but going by the fact that Haldor is nowhere to be seen in the Thor franchise, it's safe to assume the ordeal with Lorelei forever damaged his relationship with Sif.

7 THE EXISTENCE OF THE REAL MANDARIN

Trevor Slattery Mandarin

To this day, Iron Man 3 remains one of the most controversial MCU movies thanks to its handling of the Mandarin. Throughout most of the film, the Mandarin was established as a truly terrifying villain. However, things took an unexpected turn when the character was revealed to be a simple smoke screen, a part played by an actor hired by Aldrich Killian to give the world a villain to hate.

The twist was met with disappointment, as most fans felt Marvel had wasted the Mandarin's potential. Fortunately, that wasn't really the case. In the 2013 One-Shot All Hail The King, it was established that the Mandarin was very real, and he was furious by Slattery's portrayal of him. It's unclear whether the baddie will ever pop up in the MCU, but it's great to know he's somewhere out there, waiting to stir some trouble for our favorite superheroes.

6 WHY RHODEY DIDN'T HELP DURING THE CHITAURI INVASION

Iron Man 2 marked the big screen debut of James Rhodes as War Machine. Rhodey proved to be a valuable partner, and by the end of the film, he fully embraced his role as a superhero. Surprisingly, by the time Loki and the Chitauri came to Earth in The Avengers, Rhodey was nowhere to be seen. Given the gravity of the situation, fans wondered what had kept Rhodey from lending a hand during the battle of New York.

Thankfully, Marvel offered an explanation for Rhodey's absence in the Iron Man 3 prelude comic book. As revealed in the book, Tony did reach out to War Machine for help during the Chitauri attack. Unfortunately, Rhodey was in Honk Kong tracking down the Ten Rings at the time, and he couldn't fly all the way to New York in time. Well, that's certainly a plausible reason to miss a potentially-catastrophic event.

5 CHITAURI TECHNOLOGY BEING OUT ON THE STREETS

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The Avengers pitted Earth's Mightiest Heroes against a massive Chitauri army. Following a long and tough battle, the superhero team prevailed, and the invading alien forces were defeated. Given The Avengers' hopeful ending, it may be easy to assume everything was fine after. However, as the Netflix corner of the MCU proved, that wasn't the case. During season 1 of Luke Cage, it was revealed that a good amount of Chitauri technology had fallen into the hands of Hammer Industries.

The company used the technology to create a bullet capable of piercing Luke Cage's skin. The bullet became a popular commodity around the streets of Harlem, and it was even developed for police officers. The show ended before fans could get an idea of the impact that Chitauri technology could have on Harlem moving forward, but we'll hopefully see more of that in Luke Cage's second season.

4 CAPTAIN AMERICA'S SECRET AVENGERS

Civil War was a turning point for Steve Rogers. By the end of the film, the Super Soldier retired his signature shield and left the Avengers behind to adopt a more clandestine lifestyle. Unsurprisingly, a large number of fans were eager to learn what Rogers had been up to while laying low. Fortunately, Marvel offered a glimpse into Rogers' days as a fugitive in the Infinity War prelude comic book.

The book revealed that, during his self-imposed exile, Steve assembled a Secret Avenges team consisting of Sam Wilson and Natasha Romanoff. Together, the squad saved innocent people and stopped terrorist cells around the world (without drawing too much attention to themselves). The concept was fascinating, so hopefully Marvel will delve deeper into Captain America's Secret Avengers adventures at some point in the future.

3 THE SOUL STONE IS THE MOST POWERFUL INFINITY STONE

The Infinity Stones have played a major role in the Marvel Cinematic Universe for the past 10 years. So far, five stones have been introduced in the franchise, but there's one that Marvel has kept particularly close to its chest: the Soul Stone. Given the thick layer of secrecy surrounding Infinity War, figuring out the stone's backstory or location proved to be a remarkably difficult endeavor, even to the most dedicated of fans.

Surprisingly, Marvel decided to share an important piece of the stone's backstory in the Infinity War comic prelude. While discussing the Infinity Stones with Doctor Strange, Wong stated that, even though all the gems were extremely powerful, the Soul Stone may be the most powerful one of them all. The comic didn't offer more insight into the Stone's power, but for the Avengers' sake, let's hope Thanos never gets his hands on the Soul Stone.

2 S.H.I.E.L.D.'S INVOLVEMENT WITH MAN-THING

man-thing art adams

S.H.I.E.L.D. played a pivotal part in the MCU throughout most of Phase One, but its role drastically changed in Captain America: The Winter Soldier. In the film, Steve Rogers discovered S.H.I.E.L.D. had been overrun by Hydra, and he set out to destroy the organization. S.H.I.E.L.D. eventually crumbled, and all of its secrets were leaked online. The film didn't delve into the organization's various secrets, but fans got a taste of them during season one of Agents of S.H.I.E.L.D.

In the episode "Nothing Personal," Maria Hill mentioned she had appeared before Congress to explain S.H.I.E.L.D.'s leaked secrets. Surprisingly, one of those secrets was the fact that, at some point in history, S.H.I.E.L.D. had encountered Man-Thing, a popular Marvel superhero. The episode didn't delve into what had happened between the organization and Man-Thing, but it was nonetheless great to get an idea of S.H.I.E.L.D.'s covert dealings with mysterious superheroes.

1 T'CHALLA'S LONG SUPERHERO CAREER

Captain America: Civil War marked the big screen debut of Black Panther. In a way, the film served as an origin story for T'Challa, as it explored the tragic events that led him to become king of Wakanda and introduced audiences to the concept of Black Panther. Still, despite the deep dive into T'Challa's world, Civil War left audiences with a major question: when exactly did T'Challa become the Black Panther?

Fortunately, Marvel provided an answer through its 2017 Black Panther prelude comic book. According to the comic, T'Challa actually became Black Panther a week before Tony Stark went public as Iron Man in 2008, meaning that, by the time Civil War happened, T'Challa had been a superhero for the better part of a decade. That certainly explains how he was able to keep up with seasoned warriors like Captain America and Bucky Barnes.