The Sentry is one of the more interesting takes on Superman created by Marvel Comics, but why is it that he is so often forgotten by both Marvel fans and comic book creators alike?
Superman is considered one of the most well-known superheroes in the world, and though Marvel Comics cannot use the character outright, they have created several Superman "stand-ins" to use in their own stories. While some of these "stand-ins" predate The Sentry by several years, The Sentry is unique in that he actually has a long history in the Marvel continuity. Robert Reynolds, after ingesting a secret formula, gained the "Power of a Million Exploding Suns," granting him a wide array of Sentry powers including super-strength, flight, and firing energy blasts. The Sentry was active as a Super-Hero long before the Fantastic Four, and fought a wide array of villains, including his arch-nemesis The Void. The Sentry eventually found allies of his own: a sidekick named Scout, a robotic assistant named C.L.O.C., and even a pet superhero named Watchdog. So what happened?
The mystery of The Sentry begins in his debut series, The Sentry, written by Paul Jenkins with art by Jae Lee. The series opens with Robert Reynolds, appearing to be a delusional alcoholic. Eventually, he slowly starts to remember his past life as a superhero, as well as his arch-nemesis The Void. When an apparition of the Void appears before Robert, he suits up in a yellow tracksuit with a blue cape, and sets out to solve the mystery of why he forgot his true role in the first place.
As Robert comes into contact with various heroes, including Reed Richards, the Hulk, and Spider-Man, it becomes apparent that no one in the world remembers him, as various magazines, figures, and merchandise are all erased from the public's collective conscious. Slowly but surely, the wider world begins to remember The Sentry... but as a result, The Void also begins to grow stronger as well. Eventually, The Void decides to finish the fight with The Sentry once and for all, and confronts the hero in New York City. During the climactic showdown between The Void and The Sentry, the truth behind The Sentry's amnesia, as well as the rest of the world's, was revealed.
Reed Richards, during a conversation with Doctor Strange, comes to remember that The Void and Robert Reynolds were actually one and the same person. The Void acted as a separate personality from Robert, and acted to harm as many people as The Sentry saved. Eventually, The Void grew too powerful, and killed hundreds of thousands of people, and injured his sidekick Scout, leaving him crippled. Robert, Reed Richards, and Doctor Strange then come up with a way to make the world forget The Sentry, using technology to wipe the memories of everyone on Earth (including Robert himself).
The hope is that by suppressing one aspect of Robert -- The Sentry -- that the other side would be suppressed as well. While the trick worked for years, eventually it faded, leading to everyone remembering both The Sentry and The Void again. But despite Robert regaining his old life as The Sentry, he made the heroic sacrifice to wipe everyone's memory again to stop The Void from wreaking any more havoc on New York City.
The Sentry eventually re-emerged during Brian Michael Bendis' run on the New Avengers comic. Though the rest of the world still forgot who he was, with help from The Avengers, X-Men, and Emma Frost, Robert was able to safely operate as The Sentry once again. However, The Void would eventually reemerge, and continue to torture The Sentry for several years, taunting him as to which of the two were the "real" Robert Reynolds. During the Siege of Asgard, where Norman Osborn attempted to invade Asgard, The Sentry killed Ares, the God of War, and eventually went on a rampage attacking all parties involved in the battle. Eventually, both The Void and Sentry are killed by Thor in combat, with the Sentry and Robert Reynolds dying as a villain, rather than the hero he always tried to be.
Years later, The Sentry was revived in the pages of Uncanny Avengers, and was later helped by Stephen Strange, with the Sorcerer Supreme managing to keep The Void at bay. Most recently, The Sentry appeared in the Annihilation: Scourge event, which ultimately left the character in the Negative Zone, and though he may be in another dimension for the moment, The Sentry and The Void always manage to return.
The Sentry is a somber character, a noble hero who effectively destroys his own legacy to save the world, and ultimately suffers for his heroism. Despite this, The Sentry has plenty of great characteristics, similar to Superman, in that he has a knack for heroism, never surrenders, and is able to overcome insurmountable odds, even at his own expense. The fact that he was retroactively made one of the original Silver Age heroes also granted him a history of friendship and admiration from the other Marvel Heroes. One comic, The Age of the Sentry, even gave him a status quo similar to Superman's, with Robert working as a mild-mannered writer, albeit at an Encyclopedia company rather than at a newspaper, who was always going on fun adventures as The Sentry. While a character like The Sentry might not be as well known as Superman, he has proven time and again that he is more than another Superman clone, and is most definitely a hero worth remembering.