In the latest Marvel Zombies series Resurrection, the zombie virus arrives on Earth thanks to the corpse of Galactus, a monumental trap which turned many of the Earth's mightiest heroes when it was investigated in space. While this story's horror is just beginning, the original Marvel Zombies patient zero was a different kind of unexpected arrival, coming in the form of the unstable Marvel Comics Superman - the Sentry.
When the Marvel Zombies universe was introduced in the Ultimate Fantastic Four series, the infection had already consumed their home planet, with most of the Earth's population devoured or converted. With a dwindling number of survivors, the subsequent spin-off series by Robert Kirkman and Sean Phillips continued where that story left off and eventually released a prologue issue that detailed the events of the initial infection. Among the chaos and carnage, the stories hinted that the virus was brought by an unknown superhero from another dimension. In the 2007 inter-company crossover Marvel Zombies vs. Army of Darkness, Evil Dead's Ash Williams death somehow sent him to the Marvel Zombies universe on the day where it all began.
Convinced the upcoming undead invasion was thanks to the Deadites and his old enemy the Necronomicon, Ash's warnings were mocked and ignored by the Avengers, who eventually had Spider-Man web him up and take him away. Asked what he saw when he died, Ash reveals his trip through the pearly gates was interrupted by an undead superhero devouring the righteous. Revealed to be a zombie Bob Reynolds, the Sentry shrugged off Ash's shotgun blast and somehow knocked him out of the afterlife and into the original Marvel Zombies dimension. Ash learns that the Sentry followed him to this universe, appearing in Times Square where he gruesomely attacks and infects members of the Avengers who arrive on the scene.
Appearing in Sentry #1, Robert Reynolds learned not only that he had the ability of molecular absorption but that he was also a powerful hero called the Sentry who had been erased from history. With his flowing cape, "S" insignia, and unparalleled power, Sentry was quickly taken as Marvel's pastiche of Superman, even as his enemy the Void - an alternate personality dedicated to undoing his good deeds - made Sentry a dangerous and unpredictable hero. In fact, Sentry is so powerful that the heroes theorize he punched his way into their reality, mad with hunger.
Because of the Sentry, the Marvel Zombies infection continued to spread throughout the world, proving to be lethal to the general populace and infecting any super-powered individuals regardless of their powers, origins, or circumstances. Later stories attempted to explain the Sentry, who was not seen after his initial appearance, as being the result of a time loop that attempted to contain the Marvel Zombies plague within the two universes it had consumed. Although other series would bend and twist this logic for their own purposes, it's horrifying to consider that Marvel's kinda-Superman, a DC symbol for truth, justice, and hope, would actually be the harbinger of death for an entire universe.