After seeing God accept offerings from his brother Abel but decline his own, Cain, the first son of Adam and Eve, became jealous and killed him, thus becoming the first human to commit the sin of murder. As a punishment, God made him Walk the Earth forever. As this story is firmly imprinted in popular culture, Cain is a recurring character in various media other than The Bible.
He is typically The Atoner. He is immortal in every single incarnation, and sometimes he is also a Walking Wasteland, a restless wanderer, and any harm done to him is avenged sevenfold. Usually seen as the very first Biblical Bad Guy that is human, sometimes is seen on the good side in God Is Evil stories where he was framed up or he rebelled against God. Some realistic myths make him the first murderer in human history. And some others... that Cain never was the bad guy, but his brother Abel. In the stories where Cain is the good guy, expect him to be more of an Anti-Hero.
Sub-Trope of Biblical Motifs and Biblical Bad Guy. See also Cain and Abel (the original Red Oni, Blue Oni), Cain and Abel and Seth (where a third (and sometimes unknown) sibling appeared), Name of Cain (characters named after this character), The Descendants of Cain (offsprings or followers that continue Cain's path or fate), and Names To Run Away From: Biblical Names (to other names that inspires fear as Cain).
- DC Comics has Cain as a character that appeared decades ago and is integral part of the DC Magical/Dark Universe along with his brother Abel, who had less revelevance than his brother.
- These versions of Cain and Abel were originally created for the horror anthology comic House of Mystery in The '60s as one of the hosts of the magazine until its cancellation, being both brothers living in the aforementored house and who presented the stories to readers.
- Alan Moore used them in his Swamp Thing run, expanding their story and giving them an origin about why they're hosts for the House of Mystery series, being Abel revived in Earth and later his brother Cain to be their hosts.
- Plop, a humor/horror comic, has Cain, Abel, and a female character named Eve as the "hosts". Cain and Abel are probably intended to be the same characters from House of Mystery, though this was never explicitly stated.
- The Sandman features both Biblical brothers again as characters in the Dreaming and associates of Morpheus. Cain is a violent man who is prone to murdering Abel, which is a cycle they repeat ad nauseum. When Dream came back to Earth, both brothers healed and served him, being Abel his messeneger between Dream and Lucifer, as well other services they made for him.
- In The DCU, Vandal Savage is eventually revealed to be the man who inspired the story of "Cain". Depending on the Writer, Savage can be the real Cain who survived many centuries as well being one of his aliases, all thanks to his immortality. Of course, Vandal never met House of Mystery's Cain before.
- The Multiversity: In Society of Super-Heroes: Conquerors of the Counter-World #1, Vandal Savage of Earth-40 is heavily implied to be Cain, with the meteor that gave him his powers being the rock that he used to kill Abel.
- The Strange Talent of Luther Strode is about the eponymous character gaining superpowers thanks to the "Hercules Method" based on a Religion of Evil, made by noneless than Cain himself who's alive and is the Big Bad of the story.
- In The Unwritten it's pretty clear that Pullman is Cain as well as some other mythological bad guys.
- In Vampirella, Cain appears as character, who is not only revealed to be a sympathetic figure but also Vampirella's father.
- He Never Died features Cain as the main protagonist, still alive in the modern day.
- Beowulf antagonist Grendel is sometimes portrayed as Cain in later adaptations. What we have of the original was rewritten to include Christian elements, so this isn't particularly surprising (though the wording it uses would be more straightforwardly interpreted as Grendel being one of The Descendants of Cain).
- Cain, by José Saramago, plays with this. Since God has ordered that Cain cannot be harmed by any living being — including Himself — Cain gets to live through all of the Old Testament, bitter at being turned into the first murderer because he, unlike his brother, didn't want to spill blood to appease God, and horrified by the events of the OT becomes convinced that God Is Evil. He spends a lot of time calling the old man out, before eventually hitching a ride on Noah's ark. When all of humanity but God's chosen survivors have drowned, Cain takes out Noah and his family Slasher Movie style, leaving God alone with an empty world. End of creation.
- In Demian by Hermann Hesse, Max Demian defies Cain's characterization as a Biblical bad guy, insisting that Cain was a special figure whose Mark was really talent or intelligence that set him apart from than the people around him, who ultimately slandered and exiled him out of resentment.
- Kane, by Karl Edward Wagner, has the titular character as a Conan-esque version of the Biblical Cain, with stories that take place in a dangerous and dark prehistory. Kane himself was cursed with immortality by an insane elder god after having strangled his brother, Abel (or half-brother, as he at one point claims that Eve was his step-mother, which suggests his real mother was Lilith). From the evidence given in the stories, it's pretty clear that the insane elder god is meant to be Jahweh, i.e., God.
- "La Conscience" (an 1853 poem by Victor Hugo, part of the La Legende des siecles collection) tells of Cain and his family fleeing from God's wrath.
- Lucifer (2016): Cain shows up in Season Three as Lt. Marcus Pierce. Whether or not he proves to be a villain or have had a HeelFace Turn over his long life is left up in the air over the course of the season before settling on villain in the final episodes.
- Supernatural: In the episode "First Born", Winchester brothers found Cain, who owns the "First Blade", a magical sword who kills Abbadon (the Big Bad then). Here, Cain explains to Dean about why he killed Abel in the first place: he wasn't talking to God, he was talking to Lucifer. To save his brother, Cain made a deal: his soul in Hell in exchange for Abel's in Heaven. Lucifer agreed if Cain killed Abel himself. Cain did with the First Blade and was transformed into the first Knight of Hell and trained the rest.
- Avenged Sevenfold take their name from the biblical story, and their song "Chapter Four" on the 2003 album Waking the Fallen is based on it.
- Barón Rojo: "Hijos de Cain" (Sons of Cain) is about Cain being the first rebel against God and being cursed because of that, being their successors (the narrator included) known as the "Sons of Cain".
- Nautilus Pompilius: "My Brother Cain" is a song about him or another person with this name.
- The World of Darkness: Vampires suffer from the curse of Caine — all of the clans are fathered by the sons of Caine, who is implied, if not outright stated, to be the original Cain who murdered his brother. Caine is around too, and is the first vampire. Rules for fighting him are provided, but they consist of "You lose," because any damage done to him is instead reflected back sevenfold, in accordance with God's curse upon him. Vampire: The Masquerade refers to vampires as "Cainites" after Caine, who is referred to as the first vampire and is depicted in the vampire mythology as the Messianic Archetype who righted wrongs and punished the wicked. In Demon: The Fallen, it's noted that Caine invented murder and the killing of sentients.
- Warhammer 40,000: The daemon sword Drach'nyen (essentially an Eldritch Abomination currently choosing to be in the shape of a sword) was supposedly born when the first human deliberately murdered another, making it all but explicit they were talking about Cain.
- Cain by Lord Byron tells the story of Cain and Abel but through Cain's eyes. Being the Trope Maker for that trope, Cain is interpreted as a Byronic Hero and Anti-Hero, viewing him as symbolic of a sanguine temperament, provoked by Abel's hypocrisy and sanctimony.
- Sera Myu has Cain the Dark who is the biblical Cain as a spirit possessing Sailor Astarte and later a homunculus made for him.
- In Assassin's Creed II, it's revealed in the optional glyphs that Cain killed Abel over a Piece of Eden and was the founder of the Templar Order.
- Command & Conquer: Tiberian Series: It's hinted at that the Nod commander Kane is... Cain. Evidence for indicates that he is shown to be the same age during the 1940s, he survives an Ion Cannon blast that he embraces and when assumed to be be the Biblical Cain by followers does not deny it. Command & Conquer: Renegade confirms it, since you find Abel's tomb beneath the Temple of Nod. In the rather poorly received final chapter known as Command & Conquer 4: Tiberian Twilight, it is revealed that Cain is actually an alien stranded on Earth for the past thousands of years, and has likely shaped the advance of civilisation to reach a point when he can leave the planet. He phones home at the ending, leaving through a portal left by a failed Alien Invasion.
- Devil Survivor: Naoya, the protagonist's cousin, turns out to be a reincarnation of Cain. He claims that his killing Abel was a plot orchestrated by God, and his motivations revolve largely around getting revenge on God for this.
- Vampire: The Masquerade Bloodlines: Cain(e) is alluded to. Apparently, he spends his eternal afterlife working as a cab driver in Downtown LA. Playing as a Malkavian, you realize this when you eventually meet him. You would Go Mad from the Revelation, but, y'know, you already are.
- SCP Foundation: SCP-073 is the Biblical Cain, still laboring under his curse; the soil becomes dead and sterile where he walks, anything made of plants corrodes upon contact with him, and any attempt to harm him is completely reflected back. Abel is also present as SCP-076. Interestingly, Cain is quite a nice person while Abel is a homicidal psycho.