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Who is The Sentry? The new MCU hero explained

Steven Yeun is set to play The Sentry in MCU's Thunderbolts. Here, we uncover Bob Reynolds' superhero life and his evil alter ego, The Void.

Who is Sentry? The MCU hero explained: Steven Yeun and Sentry

Who is The Sentry? If you ever wanted a middle-aged hero with a dog and an evil alter ego, Sentry’s your guy. Or, rather, Bob Reynolds is your guy. And after two decades of existing on paper, he’s finally coming to the MCU!

The MCU‘s Thunderbolts is still a while off, but we’ve recently had a major casting announcement dropped on our laps that reveals the upcoming Marvel movie will include a Marvel character never seen before on the big screen. While we wait for the Phase 6 movie to arrive, here’s everything you need to know about The Sentry, the hero with some serious inner turmoil.

Who is The Sentry?

The Sentry (AKA: Robert Reynolds) is Marvel’s answer to Superman, and gained his powers from a serum that gave him “the power of a million exploding suns.”

Sentry was created by Paul Jenkins and Jae Lee, and made his first comic book appearance in his self-titled Marvel Knights miniseries back in 2000.

Since then, he’s popped up across other miniseries, one-shots, and arcs that have seen him team up with the Fantastic Four, Spider-Man, the X-Men, and the Hulk. He was also a member of the New Avengers in 2005.

Who is Sentry? The MCU hero explained: Sentry flying in the comics

When Jenkins and Lee came up with the idea for Sentry, they decided that they would create a fake history for the character, portraying him as a long-forgotten Marvel hero in need of a reboot. The plan was to weave him into the Marvel Universe history as far back as the 1940s, with renditions of him in each era.

They also decided they would come up with a fake publication history, including alternate versions of themselves as his creators, known as Juan Pinkles and Chick Rivet, which were anagrams of their own names. Eventually, they pitched the idea to the Marvel Knights editor Joe Quesada, who commissioned the miniseries.

Who is Sentry? The MCU hero explained: Sentry with his arms crossed

Sentry’s origin is a strange one, as he began his Marvel life as a middle-aged, out-of-shape man known as Robert ‘Bob’ Reynolds. Bob had his memory wiped, and no longer remembers that he’s one of the most powerful heroes around.

Bob first got his powers when he — a drug addict at the time — broke into a lab to find a supply. He ended up taking a mysterious substance which ended up being Golden Sentry Serum. Not unlike Captain America’s Super-Soldier serum, this transformed Bob and gave him unparalleled cosmic powers.

Over time, Bob recovered from his addiction and went on to become Sentry, one of the most powerful Marvel characters in the canon. So, why did he forget who he was? Well, it all has to do with The Void.

Who is Sentry? The MCU hero explained: The Void floating

Who is The Void?

The Void is a dark entity that became physically connected to Bob/Sentry when he got his powers, and is essentially his evil alter ego.

If it sounds like a Dr Jekyll and Mr Hyde situation, that’s because it is. When Bob ingested the serum, he ended up developing a physical connection with a being known as The Void. Destructive, evil, and chaotic, The Void becomes Bob’s ongoing nightmare.

In this sense, Bob’s greatest enemy is himself, since he is unable to control The Void when it wants to take over. He’s both a hero and a Marvel villain of epic proportions. At first, Bob doesn’t know that he’s connected with The Void until it attacks New York City and ends up killing over a million people.

Who is Sentry? The MCU hero explained: The Void with dialog in comics

When he realizes The Void is in fact him, he decides to erase all memory of his existence. If he’s unaware of his own powers and history, then The Void can be controlled. Thanks to Doctor Strange and Reed Richards, Bob erases his entire past and Sentry is forgotten. (We’re getting No Way Home flashbacks right now.)

This is where things get a little repetitive, because Bob eventually regains his memory. The Void starts to make a reappearance in flashes, so Bob then goes on a quest to track down each one of his Marvel buddies to find out why he’d erased his memory and existence. (We’re getting the band back together!)

After enlisting their help, Bob realizes the truth and makes the painful choice to erase his existence from the rest of the world again, knowing it’s the only way to stop The Void for good. In the final panels of this particular arc, it’s left open-ended as to whether Bob still remembers himself or not.

Who is Sentry? The MCU hero explained: Sentry with dialog in comic book

Is Steven Yeun playing The Sentry?

While it hasn’t been officially confirmed by Marvel, the news that Steven Yeun would be playing The Sentry was leaked in November 2023 by none other than Robert Kirkman.

Yeun currently stars in Kirkman’s animated series, Invincible. The news of Yeun’s Thunderbolts role came when Kirkman shared [via David Finch] that Yeun had called him during some very important prep work for the character.

“My good friend Steven Yeun is playing the Sentry in a movie. Yeah, he called me, he went in for a costume fitting,” Kirkman said. “…He called me and he said, ‘I just came back from a costume fitting for the Sentry. I guess I only do superheroes that are yellow and blue.'”

So, the cat’s out of the bag. At least it is if we take Kirkman’s word for it. We expect Marvel to confirm the role officially over the next few weeks, so we can soon start getting really hyped.

Who is Sentry? The MCU hero explained: Sentry surrounded by lightning

The Sentry’s powers and abilities explained

The Sentry is one of the most powerful heroes in Marvel, thanks to the Golden Sentry Serum that changed his molecules. 

The Golden Sentry Serum is said to be a hundred thousand times stronger than Captain America’s Super-Soldier serum. Basically, there’s not a lot this guy can’t do. He’s also said to hold back on his full powers a lot of the time — humble guy.

His main skill would be intense super-strength, but he also possesses superhuman speed, advanced senses (he himself has said that he can hear a heartbeat of a butterfly in Africa while he’s in the US), and can absorb energy from any source, anywhere.

He can also regenerate quickly, since his molecules are able to be recreated almost instantly from any kind of damage. But his strangest ability is that the serum transformed his molecules to exist ahead of the current timeline, which basically means that Sentry exists in the past, present, and future, all at once.

So, he has unlimited cosmic power, is virtually indestructible, and doesn’t even typically flex his full capabilities. On top of all this, Sentry also has a team behind him that includes Billy Turner (known as Scout), who also inherited powers from the serum, and his dog, Watchdog. Watchdog is a Welsh Corgi who always obeys, and is frankly the cutest sidekick we ever did see.

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The Sentry in the MCU explained

Thunderbolts will  be The Sentry’s first on-screen appearance since he’s only appeared in comic books and video games until now.

With that in mind, it’s easy to see why everyone’s getting so excited about him making his MCU debut. His lack of on-screen history makes sense — compared to some of Marvel’s other heroes, he’s not been around very long.

If Yeun is, in fact, playing Sentry in the new movie, then we think he would serve as the antagonist for the Thunderbolts. Since The Void is such an integral part of his character, we expect Marvel would want to play on this dual personality element and have the Thunderbolts try to take down The Void while still trying to save Bob.

That’s Sentry! To prep for all the Marvel flicks soon to come, revisit the Marvel movies in order, and see what’s left in Marvel Phase 5. You can also check out all the Marvel series, and keep tabs on our guides to Deadpool 3 and Captain America 4.

We’ve also got a list of the best movies of all time for some real classics. Oh, and don’t miss our The Marvels review, and check out our feature on why Marvel needs to learn that killing characters isn’t everything.