The many heroes and villains of Marvel Comics often find themselves wrapped up in mysterious plots where life and death hang in the balance. Lawyers, detectives, and villains alike sometimes land in whodunits that leave readers scratching their heads and theorizing lists of usual and unusual suspects. Sometimes the mystery is hidden in plain sight, overlooked by readers who are used to suspending their disbelief and not asking questions.

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These mysteries are among the best in Marvel Comics, often dealing with murder, identity, and items or beings of mysterious origin. There are hundreds of secret identities and clandestine schemes between the pages, which slowly fan the flames of readers' curiosity until their eventual resolution. What makes these mysteries the cream of the crop is their impact on the rest of the Marvel Universe on the whole, and the lasting impact they've made on classic characters.

9 Doctor Strange Solved His Own Murder

Strange explains his plan to bring classic Dr. Strange back upon his death

In issue one of Death of Doctor Strange, written by Jed MacKay, with pencils and inks from Lee Garbett, colors by Antonio Fabela, and letters by Cory Petit, readers become witnesses. Someone knocked on the door of an exhausted Stephen Strange, and when the Sorcerer Supreme went to answer, a malevolent grin told him he would die.

Not long after Strange’s disappearance, supernatural forces descended upon the world, causing trouble for Marvel's heroes worldwide. While shorter than some of Marvel’s bigger mysteries, Death of Doctor Strange proved a fresh take on the classic whodunnit where the lead investigator was also the victim.

8 Red Hulk Kept His Real Identity Hidden For Years

Red Hulk stands in his own mysterious shadow

When Red Hulk first appeared, his identity was completely unknown. The brute's motives and manner of speaking provided clues as he rampaged through the Marvel Universe, causing problems on a cosmic level. While many theorized about his true identity, two years went by before the answer was revealed.

Thaddeus "Thunderbolt" Ross had always been obsessed with the Hulk, so it made sense that he had studied how the Jade Giant worked. By becoming what he'd vowed to destroy, Ross gained an unending supply of rage from his self-disgust. In the end, this mystery's resolution was a tragic portrait of a man who let rage win.

7 Buried Alien Was A Different Kind Of Mystery

Buried Alien in Marvel Comics

When the fastest beings in the universe gathered for a race across the cosmos, readers placed their bets on the heroes and villains of the Marvel Universe. During the event in Quasar #17, written by Mark Gruenwald with art by Mike Manley, colors by Paul Becton, and letters by Janice Chiang, a bolt of lightning struck the track and a stranger in tattered clothes outpaced everyone.

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Buried Alien didn't know who he was or where he came from. Coincidentally, Barry Allen, DC Comics' Flash, had just passed away. Buried Alien's mysterious origin was never fully solved within Marvel Comics, but readers understood that his appearance and his victory proved that Barry Allen was the fastest, in every universe.

6 Captain America Was An Agent Of Hydra

Captain America saying Hail Hydra in Marvel comics

In Captain America: Steve Rogers #1, written by Nick Spencer with art by Jesus Saiz and letters by Joe Caramagna, two simple words sparked a mystery that would rewrite years of Marvel history and operations. After fighting Nazis alongside other star-spangled heroes, Cap turned on his allies and revealed that he'd been working for Hydra all along.

Naturally, with the leader of the Avengers revealing himself as a villain, the whole of the Marvel Universe was turned on its head. Steve Rogers also served as director of S.H.I.E.L.D. during this time, leading to the world-threatening crisis: Secret Empire. Despite its lack of staying power, the series gave Marvel's fans a bizarre mystery to unravel, since it seemed impossible that Cap could be a traitor.

5 Spider-Man's Black Suit Was Alive

Black Suit Spider-Man reveal in Marvel Comics Secret Wars

Secret Wars featured the planet Battleworld, where Spider-Man damaged his suit in combat. Using a mysterious alien machine, he created the black suit that readers today call the Symbiote Suit. At the time of the suit's creation, however, the true nature of its "fabric" was entirely unknown.

After returning to Earth, Peter Parker was different. He became more irritable, and his home and school life were on a steady decline. Battling bouts of rage, Peter eventually sought help and, alongside members of the Fantastic Four, learned the suit's true nature. The suit was a living alien lifeform that was taking over his body. When Peter rejected it, it bonded with Eddie Brock to become Venom.

4 Wolverine Worked To Piece Together His Past And Identity

Wolverine with tattered costume

James Howlett, or Logan, is best known as Marvel's Wolverine. He's the best there is at what he does, but he often prefers to do it alone. For having lived such a long and action-packed life, there's a lot about the three-clawed hero's life that remains a total mystery.

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Is Wolverine related to Sabretooth? Did he have a family before? Is he a homo superior or a canine-humanoid offshoot? How do samurais play into all of this? All these questions have surrounded Wolverine for decades, but what makes them such great mysteries is Logan's perseverance through uncertainty.

3 Someone Killed Uatu The Watcher

Uatu lies dead on the moon

Uatu the Watcher is a mystery to the characters within Marvel Comics, but he's been known to speak directly to readers when examining alternate timelines and significant events. When the being who sees everything is taken by surprise and murdered, some of Earth's mightiest heroes assemble on the moon and begin investigating.

Everyone in Original Sin, a universe-wide event that reached most of Marvel's popular titles at the time, was a suspect. The murder was carried out without any physical evidence and for motives unknown to those involved. This mystery was a perfect "whodunit," drawing inspiration from the pulp mystery comics in Marvel's past.

2 The Hobgoblin Had Spider-Man Running In Circles For Decades

Hobgoblin laughing menacingly from the Spider-Man comics

Introduced in Amazing Spider-Man #238 by Roger Stern, John Romita Sr., Andy Yanchus, and Joe Rosen, the Hobgoblin appeared to be a revival of the Green Goblin, but his identity remained secret. Three writers worked on the villain's story arc, each with different plans for his identity, resulting in an unpredictable fifty-one-issue journey.

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The many twists and turns surrounding the Hobgoblin's true identity likely resulted from the shuffling of creative minds that built up his big reveal. Given Norman Osborn's recent death and the rise of Harry Osborn, many fans focused on Harry and ignored Ned Leeds, a new character who wasn't terribly important and was supposed to be dead. Of course, there were more layers to that mystery, even if the writers didn't know it at the time.

1 No One Knew Who To Trust After The Skrulls Invaded

Marvel Heroes as skrulls during Secret Invasion by Marvel Comics

Secret Invasion affected every Marvel title when it came out in 2008, revealing an evil plan that had been in motion for years. Slowly, one by one, Earth's heroes learned that Skrull invaders had replaced some of them. As mistrust grew between the characters, readers had to stay sharp and on the lookout for imposters.

The mystery of which heroes had been replaced spread throughout all of Marvel's titles. S.H.I.E.L.D. was infiltrated and X-Men and Avengers had been replaced months before the event started, unbeknownst to readers. This mystery was well executed and planned out, and the way it perplexed readers and classic characters alike cemented it as one of Marvel's best mysteries of all time.

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