- "Disease gets a bad rap, don't you think? For being filthy; chaotic. But, really, that just describes people who get sick. Disease itself... Very... pure... single-minded. Bacteria have one purpose - divide... and conquer. That's why, in the end... it always wins! So, you've got to wonder why God pours all his love into something so messy! And weak!! It's ridiculous. All I can do is show him he's wrong, one epidemic at a time!"
- ―Pestilence's views of disease and humanity.[src]
Pestilence is one of the Four Horsemen of the Apocalypse, who is responsible for disease and sickness in the natural order. Pestilence manifested and was controlled by Lucifer for the Apocalypse and was responsible for a scheme to cause a pandemic of the Croatoan virus, but the plan was thwarted.
As the horseman who manages and embodies plague and disease, Pestilence has control over and can manipulate viruses, infestations, plagues, ailments and other sicknesses, and he is a force of nature embodied and a very powerful being. Pestilence could manipulate his own human form to make it extremely sickly so he could spread diseases such as swine flu naturally, he could infect humans with specific diseases through just a touch, and when Pestilence activated his ring, his mere presence would cause any humans within a specific radius of him to instantly fall cripplingly if not fatally sick. Pestilence's disease-inducing powers could also affect graceless angels' vessels. (Hammer of the Gods, Two Minutes to Midnight)
Pestilence could be identified through several methods. One was that his human form didn't properly show up on camera, with CCTV showing static over uncovered parts of Pestilence's human body such as his hands and head. (Two Minutes to Midnight) Another was that since he was pestilence itself, decay and sickness tended to attract to him, in the form of massive swarms of flies gathering to him. (Hammer of the Gods)
While Pestilence, as a force of nature embodied, couldn't be killed, he did still require his ring for channeling his powers and abilities on the Earth, and so he could be incapacitated by separating him from his ring. (Two Minutes to Midnight)
According to the Book of Revelation and the prophecy of the Apocalypse, Pestilence would rise with the other horsemen when Lucifer walked the Earth, and would serve as one of Lucifer's primary weapons for his genocide against humanity. Pestilence would ride across the lands, spreading sickness, diseases and pestilence wherever he went, and eventually also unleashing the Croatoan virus upon the world. (The Devil You Know et al.)
Pestilence has existed throughout time as a force of nature, and his effects have been felt by humanity throughout history in the form of humans' weakness towards sickness, irritation and disease. (Supernatural: The Official Companion - Season 5)
In 2009, when the Apocalypse began after Lucifer was freed from his cage, Pestilence and the other three horsemen manifested on Earth in human form to act as Lucifer's weapons against humanity; having been bound by Lucifer to be where he wanted, when he wanted. (Supernatural: The Official Companion - Season 5)
In the following year, Pestilence was passing through towns and areas in the form of an ordinary driver on the road, causing outbreaks of swine flu everywhere he went and creating an epidemic. (Hammer of the Gods, The Devil You Know) However, the swine flu outbreak was merely the catalyst for Pestilence's endgame: to spread the Croatoan virus across the country by hiding it within swine flu vaccines that were to be distributed in response to the epidemic. (Two Minutes to Midnight) For this purpose, Pestilence had demons under his command, led by Brady, infiltrate the medicine company Niveus Pharmaceuticals to initiate a simultaneous nationwide distribution of Croatoan-laced vaccine stocks. (The Devil You Know)
While Pestilence was hiding at the Serenity Valley Convalescent Home in Davenport, Iowa, disguised as Dr. Green, so he could use the elderly patients under his care there as test subjects for his experiments with diseases and pathogens, he was tracked down by Sam and Dean Winchester, who had obtained his location from a captured Brady. When Pestilence became aware of the Winchesters' arrival, he rebuffed his assistant's advice that they flee, as he wanted revenge on the Winchesters for what they'd done to War and Famine.Pestilence proceeded to activate his ring against the Winchesters, causing everyone nearby to instantly fall cripplingly ill, and rendering Sam and Dean too sick and agonized to fight Pestilence once they found him. But before Pestilence could torture the Winchesters any further, Castiel arrived to help. Though Cass was affected by Pestilence's powers due to having used up his angelic power, while Pestilence was gloating, Cass managed to take him by surprise and cut off his fingers with the demon-killing knife. Separated from his ring since it was on one of his cut-off fingers, Pestilence's effect immediately wore off and Pestilence himself vanished; though not before declaring that it was too late anyway, since his plan with Niveus and the Croatoan-laced vaccine was still in operation. (Two Minutes to Midnight)
It is unspecified what happened to Pestilence after he lost his ring, but it is presumable that he would have been weakened and reduced to a catatonic husk without it, as War and Famine had been. (The Devil You Know) Shortly after Pestilence's ring was captured, his plan with the Croatoan virus was derailed when Sam, Castiel and Bobby Singer destroyed the warehouse containing the Croatoan stocks. (Two Minutes to Midnight)
Pestilence was a being who admired the sicknes and disease he embodied, considering it very pure for how it existed solely to divide and conquer; he also intensely despised humans as "messy and weak" creatures, and was never able to understand why God loved them so much. Pestilence took a kind of cheerful glee in using living humans against their will as 'guinea pigs' for his experimentation with diseases; he tended to start up a conversation with his victims in which he took a cheery and friendly voice with them while casually letting his true colours gradually show, occasionally letting out sudden and brief explosions of anger and disgust before immediately resuming his faux friendly tone. Despite Pestilence's intense disgust and cruelty towards humans, he did have an affectionate side. He considered the other horsemen to be his family and his brothers, and he could become frighteningly seething and extremely vengeful towards anyone who harmed them. Pestilence was also comforting towards his demonic assistant Palomino whenever he'd snapped at her (which was a contrast to Pestilence's brother Famine, who had no problem at all with sacrificing his demon henchmen).
The horseman upon which Pestilence is based is described in Revelation, 6:1-2. According to Revelation, it is the first one of the Four Horsemen to be released, riding out when the first of the seven seals is opened by Jesus Christ. The first horseman is also described as riding a white horse, and as carrying a bow and arrow and wearing a crown. The white rider is generally recognized as representing Conquest, but an alternative interpretation more common to pop culture instead portrays him as representing Pestilence. Some scholars also believe that the white horseman could represent Jesus or the Holy Spirit, or on the other hand could represent the Antichrist or other false prophets.