First seen in The Sentry #1 (September, 2000), Robert Reynolds was an overweight, middle aged, alcoholic until one day he awakens and realizes that he is the Sentry, a superhero with the power of one million exploding suns, who must once again take the mantle of the hero to fight his archnemesis the Void, whom he fears is returning soon.This rather strange origin story begun via a hoax that was perpetuated by Stan Lee himself in stating that there was a golden age superhero whom he just forgot about and wanted to weave into the continuity. Through a series of recursive flashbacks Robert Reynolds is seen fighting alongside Marvel's most popular superheroes including the Fantastic Four, the Hulk, and Spider-Man, and the entirety of the Sentry's first miniseries revolves around figuring out why everyone has Laser-Guided Amnesia surrounding his existence.His actual powers were bestowed upon him when a young Robert, while working in a physics lab, drank a serum that "moved his molecules 1 second ahead of the current timeline." It was later revealed that this was a newer version of the Super Soldier serum that transformed Captain America.Seen as somewhat of an Alternate Company Equivalent of Superman due to his seemingly limitless powers, including: energy blasts, super strength, flight, and of course a hefty dose of New Powers as the Plot Demands.The Sentry while seeming like an Invincible Hero actually has many weaknesses due to his being Ax-Crazy (this is not expunged when Robert becomes the Sentry). Robert Reynolds is an agoraphobic, anxiety-ridden schizophrenic who relies on his robot sidekick CLOC to calculate the severity of problems that need his help, and solves them in order based on CLOC's input.Despite his death at the end of Dark Reign, the Sentry was resurrected by the Apocalypse Twins' new Horsemen in Uncanny Avengers, though Thor convinces him to help stop Exitar the Executioner. Sentry, having succumbed to his insanity and believing himself to be the successor of Apocalypse, agreed to do so... after he rid the world of the "cancerous" mutants.In terms of Video Games, The Sentry was a playable character in Marvel Ultimate Alliance 2 for Nintendo DS and Marvel Super Hero Squad Online.
Back from the Dead: While he's been resurrected several times, his most recent revival was when the Apocalypse Twins revived him as one of their Four Horsemen of Death. It's not known if the Void has been revived as well.
Sentry/Void: How many gods will I have to kill today?
Beware the Superman: Being powerful to such a degree is more than dangerous when also having such serious mental problems. As seen in Dark Reign, he is very easily manipulable. And not to talk about what happens when the Void breaks out. Breaking literally every bone of the freakin' Hulk, rampaging through New York or leveling the whole city of Asgard. And that's by far not everything that this psycho has unleashed during his life.
After he survives being disintegrated, Bullseye wonders if, when he finally goes over the edge, they'll actually be able to kill him. The answer is no, not unless he lets you.
Dark Secret: The truth behind the origin of the Sentry, kept between Bob and his wife, Lindy. Bob was just a drug addict looking for a fix, not an innocent young man working in a physics lab. The Void is the manifestation of the part of him that is still that junkie.
Death Is Cheap: Sentry had died and returned within the confines of a single issue, usually as a result of the Void's intervention.
Depending on the Writer: Sentry has something like eight different origins, and the level and type of his mental psychosis fluctuates from issue to issue. Even the Void seems to change from split personality to separate entity on alternating weekends. His level of power also goes up and down, from "stronger than Thor, but it'd still be a fair enough fight" to "could smash the entire planet into gravel with a single pushup."
Did You Just Punch Out Cthulhu?: The Sentry has supposedly defeated Galactus either on his own or with the help of Nate Grey. Debatable given never really shown even in a flashback and the Sentry's unreliable history.
And when Nate Grey mentioned it, he was quite possibly manipulating the Sentry, as he was in the middle of a fight with the Dark Avengers. And much like his dad and Cable, he's shown hints of being The Strategist to an insane degree.
Disproportionate Retribution: Bob finds out that some Yoga instructor is pulling some moves on his wife; sometime later, presumably, The Sentry saves 150.000 people from a crashing boat while The Void hurls a jet airliner into a building killing 150.000 people, Ramón the Yoga instructor was in that building.
Expy: His original series seems to be heavily inspired by Alan Moore's rework of Marvelman/Miracleman. Both feature middle aged guys who are vaguely haunted by their past as the most powerful person on the planet. Down to details like being jealous of their super selves, their wives being more attracted to their other selves and their origins in a secret government program. Which makes the Sentry an Expy of a reworked Darker and EdgierCaptain Ersatz of a Captain Ersatz, as Marvelman was a British copy of Captain Marvel, who was himself a copy of Superman. So he's like Superman's fifth cousin twice removed.
Lampshaded in-comic: "I don't throw everything into the sun."
Ideal Hero: The Sentry limited series reveals that the Sentry persona is actually Bob Reynolds' idealized version of himself: the handsome, invincible champion of the entire planet.
Indecisive Deconstruction: As time goes on, it gets increasingly hard to tell if his Character Shilling is part of a clever commentary on the shifting nature of reality in comics or just the writers desperately trying to convince fans that Sentry's really a likable and interesting character, honest.
What if a foe has Wolverine's healing factor and unbreakable bones and Luke Cage's unbreakable skin? Sentry won't even blink and will let the mind rape commence◊.
Multiple Choice Past: In truth, it is still not clear exactly what the relationship is between Bob Reynolds, the Sentry and the Void (Is the Void the real Bob Reynolds, or is the Sentry, or is neither, or are they both?), exactly what the serum was he took or even whether it actually did anything, what the exact nature and source of his powers is (I am a superhuman! I am actually the angel of Death! I am a refugee from another universe! I am Galactus!), how the Void really came into existence and whether he is really dead. This, of course, fits in very nicely with the notion that the Sentry is bugnuts insane and genuinely does not know what happened, and perhaps subconsciously even alters reality to suit whatever his psychosis says is the real story that day!
Nigh-Invulnerability: To an absolutely insane degree. He was bodily disintegrated by both Morgana leFay and Molecule Man, and simply re-appeared with no explanation. When he tried to commit suicide by flying into the sun, he was already swimming in superheated solar plasma when his evil self basically said "Don't be silly, kiddo".
Power Creep, Power Seep: In his miniseries, the Sentry actually bled after being bitten by a dog. By the time Siege rolled around, Bob was shrugging off blows from Thor's hammer without a scratch on him.
This could be something to do with his psychosis, as his strength levels yo-yo almost as much as Gladiator's.
Power Glows: He's not called the "Golden Guardian of Good" for nothing.
Psychic Powers: The Sentry has shown psychic powers strong enough to give Doctor Strange pause. It is believed that Bob used this power to erase the entire planet's memory of the Sentry, including his own.
Psycho Serum: The serum that gave Bob his powers was a new version of the Super Soldier serum amplified 100,000 fold. According to The Sentry limited series, Bob became the insane Void persona from the moment he injested the serum.
Split Personality: The Sentry (good) and the Void (evil). The relationship between them is described as a god complex: every time Sentry did something good, Void did something equally evil.
Strong as They Need to Be: Sentry only gets stronger with time. He cannot be completely destroyed (see his immortality trope entry) and can exchange punches with Hulk and Thor. Sentry can impress even Doctor Strange, the Sorcerer Supreme, with his psychic and telepathic abilities and possesses molecular manipulation on the same level as Molecule Man. Moving faster than the speed of light is a simple matter for Sentry and he can travel distances in seconds that even the speedier characters require minutes for. The only weakness Bob has is his unstable mind but making use of this weakness is a huge gamble even for master manipulators because they risk releasing the Void.
Sentry while either completely stable mentally or Voided out is a true monster to behold. Sentry's strength depends on his mental stability and Sentry managed to fight World War Hulk after being consumed by his agoraphobia for 29 hours, showing even a weakened Sentry is a force to be reckoned with. The Void managed to rampage through Asgard and topple foes such as Thor and Ares in Siege, and he was just getting started. When Void was not as powerful, he was still able to break every single bone in the Hulk's body.
Super Speed: Sentry can fly to the Sun and back in seconds.
Super Strength: The Sentry is one of the strongest heroes in the Marvel Universe, capable of matching strength with the Hulk, Thor, and Hercules. The Void's strength is enough to break almost every bone in the Hulk's body.
Super Weight: He is often said to be Level 6. He supposedly stalemated Galactus, has often been compared to the power of a million exploding suns, defeated a far weaker than previously Molecule Man, and was said to be a Biblical angel of death, capable of causing greater destruction than the multi-universal damage of the Scarlet Witch, but we never actually see anything concrete, beyond easily overloading the Absorbing Man, who has had no trouble copying Mjolnir in the past. As it is, he is a powerful Level 5.
Took a Level in Badass: The Void began taking on larger, more powerful forms leading up to Siege, possibly due to the second dose of serum provided by Norman Osborn. Before, during the Sentry miniseries, the Void seemed to be limited to humanoid size at best.
Unskilled, but Strong: With the Mighty Avengers, Sentry is stated outright to be the strongest member, but held back by his lack of skill.
"World of Cardboard" Speech: Gives a brief one during the events of World War Hulk. The Hulk contends that the Sentry doesn't want to fight him. The response (paraphrased): "God help me, I do...because you're the only one I can hit like this."
Your Cheating Heart: Lindy has this issue in The Sentry V2, besides preferring the Sentry persona instead of ol' Bob, she also had to cope with her husband's unstable presence by seeking an affair with her Yoga instructor Ramón.